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Analogy

Alberto Strumia

I. What is Analogy? 1. Common Meaning of the Word Analogy. 2. Analogy and Logic. 3. Analogy and Metaphysics. - II. Analogy in the Aristotelian-Thomistic Logic and Metaphysics. 1. Analogy of Attribution or Simple Proportion. 2. Analogy of Proper or Intrinsic Proportionality. 3. Analogy of Improper Proportionality, Extrinsic or Metaphorical. 4. Analogia Entis. 5. The Crisis of Analogy. - III. Analogy and Theology. 1. The Knowledge of God and Divine Names. 2. Examples of Analogy in the Scriptures. 3. Uses of Analogy in Theology. 4. Analogia Fidei. - IV. Analogy and Science. 1. Analogy alongside Scientific Theory: Analogy and Experimental Science. 2. Analogy alongside Scientific Theory: Analogy and Mathematical Science. 3. Analogy within Scientific Theories. 4. The First Steps towards a Theory of Analogy. - V. The "Profundity" of Analogy.

 

I. What is Analogy?

1. Common Meaning of the Word "Analogy". The word "analogy" in its usual sense in modern English means . Recently, the adjectival form of the world "analogy", "analog", as opposed to "digital" or "numerical", which is used in reference to two different ways in which electronic devices work, has become of frequent use. The origin of the word "analogy", as the Greek root (analoghía) suggests, is however very ancient and is based on the mathematical concept of "proportion" (a:b = c:d) which establishes a similarity based on the equivalence of relations. One may think, for instance, of the similarity of two triangles whose sides stand in a fixed relation. The transfer of the word "analogy" to  mathematics and to  logic and philosophy dates back to Plato (427-347 B.C.) who, however, never devised a theory of analogy. Aristotle (384-322 B.C.) would be the first to give a systematic formulation of it in the field of logic. In the Middle Ages,  Thomas Aquinas brought to fruition Aristotle’s work with an intention at once philosophical and theological. In successive periods, beginning with the Nominalists, analogy became, less and less understood. It was gradually abandoned in the fields of logic and philosophy, and restricted in its scope to the point of becoming a simple literary "metaphor". And it is in this sense that the term is used today in the context of hermeneutics.

2. Analogy and Logic. The need of introducing analogy in Greek thought seems to arise from two types of problems: one which is strictly "logical-linguistic" and the other more properly "metaphysical". From the logical-linguistic point of view, Aristotle, and later Thomas Aquinas, begin with the observation that in common language —which expresses and therefore is a sign the structure of how thought proceeds— the same term ("predicate") can be attributed to different subjects in a "univocal", "equivocal", and "analogous" way. In the first case, the predicate has exactly the same meaning for the entire class of subjects it is attributed to: for example, when we say and , the term "man" corresponds to the same definition "rational animal" in both instances. In the second case, on the other hand, the same term is used with completely different and uncorrelated meanings: as when one says , . In the second case, the word "bull" corresponds to different definitions in each of the two examples: in the first example, it involves an "adult male bovine", in the second, "a communication written by the Pope". Consequently, the use of the same word to signify different things is adopted purely by convention, so much that equivocity can be related to the language one uses and can be lost when one translates into another language. In the third case, finally, the same term is used with different meanings, but in a certain way they have a real correlation and therefore the use of the same term indicates a real similarity and not a mere choice of convention: for example, as when one says , . Properly speaking, only a man can be intelligent, but a theory can be said to be intelligent in so far as it is an expression and "real effect" of the intelligence of its author (and not by pure convention!).

3. Analogy and Metaphysics. The second class of problems which have led to the idea of analogy is not purely logical and linguistic, but more properly metaphysical, in that it is inherent in things and is successively transferred to thought and language with which one attempts to understand reality ( REALISM). Greek thinkers confronted the problem of reconciling two seemingly contradictory facts of  experience: the being of things and their "becoming", or in physical terms, "motion". The "monist" solution — that is, a solution based on the assumption that reality is founded on only one constitutive principle (be it material or immaterial) — requires that one take one of the two facts of experience as apparent: if one admits only the reality of being, as a single undifferentiated state, "being" can never be but itself, as it cannot change into something different from itself; on the other hand, one cannot explain the phenomenon of motion we observe in everyday experience, as the passage from one state to another. Therefore, one must say that this passage is not real but purely apparent (this is the solution proposed by Parmenides, VI-V century, B.C.). We are then left with the problem of understanding what produces this illusion in us. If, on the other hand, one admits the reality of becoming only, it is necessary to admit the contradiction that becoming, by the very fact that it is, coincides with being, that multiplicity coincides with oneness, that nothingness, that is non-being, is a state of being, and becoming is a continuous oscillation between these two contradictory states. However admitting this contradiction implies, in the end, that knowledge is impossible (this is the extreme consequence of Cratilus, following in the footsteps of Heraclitus, VI-V century B.C.). To explain human experience completely, it is necessary to hypothesize that being may exist according to "differentiated states" that constitute a spectrum of modes of being lying somewhere between being in its absolute fullness (God, Pure Act) and its complete absence (nothingness). To understand correctly the analogy of being we need the help of the accurate latin terminology: ens means "being" as a subject capable to be, while esse, is the property of "being". Being (esse) is the principle by which a being (ens) is: "being" (ens) is a term which is predicated in a differentiated but not equivocal way of different subjects.

The notion of analogy of being corresponds, from the logical point of view, to the metaphysical fact which assumes that being (esse) is actuated ("participated") in differentiated modes and degrees in the existing things. Thus, the logical theory of analogy corresponds to the metaphysical theory of participation.

 

II. Analogy in the Aristotelian-Thomistic Logic and Metaphysics

In Aristotelian-Thomistic logic, three types of analogy are possible (even if further distinctions have been introduced by later schools): analogy of "attribution", or of "simple proportion", analogy of "proper", or "intrinsic proportionality" and analogy of "improper", or "extrinsic", or "metaphorical proportionality".

1. Analogy of Attribution or Simple Proportion. Analogy of attribution is usually presented with a classic example: "Tom is ‘healthy’, his complexion is ‘healthy’, this food is ‘healthy’, the air is ‘healthy’." By observing this example, we note that the characteristic of being "healthy" is proper only to Tom who is the only subject which can be said to enjoy good health, being the only living being of the things considered in this example. One cannot properly speak of the other things as being "healthy" because they are not living beings. One can say that in a certain sense these non-living beings are "healthy" only in reference to the good health of Tom, who alone is the subject of the predicate "health" in the proper sense. For this reason, Tom is called the summum analogatum or primum analogatum.

As for the other subjects, one can single out the relationship they have with the healthy state of being of Tom: his healthy complexion is a sign of his good health, in so far as it is an "effect" of his good health. Healthy food is that which favors Tom’s good health as one of its "causes". It must be understood that the reference to the summum analogatum is neither conventional nor accidental, but is instead founded on reality and confirmed by experience (from the fact that healthy food really contributes to the good health of someone who eats such food and that healthy complexion is really a sign of good health, and so on and so forth). For this reason, food, complexion, and climate are considered analogata inferiora. It is this reference, which is founded on reality, that makes the concept of attribution more than just "equivocal". These things and realities are and remain different, but the common name of the predicate expresses qualities which, even if they are in themselves different, have, under a certain aspect, a direct relationship with the quality of the primum analogatum (cf. Thomas Aquinas, Summa Theologiae, I, q. 13, a. 5).

2. Analogy of Proper or Intrinsic Proportionality. Even this second kind of analogy is usually illustrated with a classic example which consists in comparing sight with intelligence. We often use the idea of "vision" either in reference to "eyesight" or in reference to the "mind’s understanding". Thus, we say, for example, "the light of truth illuminates the mind", "to understand at first glance", "a philosophical vision of reality". In these examples, we have a term which expresses an action (seeing) which we attribute to two different subjects (the eye and the mind). In this type of analogy, the similarity is established between the "relations" between predicate and subjects and not between different senses of the same predicate attributed to different subjects. This similarity between the relations can be summarized by a formula which recalls that of a mathematical proposition: . Nevertheless, when we write a mathematical proportion, we establish two "equal" relations (2:3 = 4:6), whereas in the case of the analogy of proportionality, we state that two subject-predicate relations are not the same, but "similar" (cf. Thomas Aquinas, De Veritate, q. 2, a. 11). It must be emphasized that the action attributed to the subjects is really connected with each of them. The faculty of seeing is intrinsic to the eye and the faculty of understanding is intrinsic to the mind: in both cases, we are dealing with a natural capacity, a proper and therefore really possessed faculty. For this reason, one speaks of analogy of "proper" or "intrinsic" proportionality. We note that in this type of analogy there exists neither a primum analogatum nor analogata inferiora: we have instead a subject-quality relationship which can be applied, in the proper sense, to a subject (the eye in the case of vision) and in a "similar" sense to the other subject (the mind). Seeing is proper of the eye, not of the mind. One can therefore say that, in a certain sense, what takes the place of the primum analogatum is not the subject to which the predicate is properly attributed, but a relation between subject (the eye) and predicate (able to see).

3. Analogy of Improper, Extrinsic, or Metaphoric Proportionality. The third type of analogy is that of the "metaphor". It involves a kind of analogy in which, unlike the two preceding cases, there is no real basis for similarity, but which is founded instead on a similarity discovered by the knowing subject who does not see any cause-effect relation in the nature of the subjects and the predicate nor any real similarity in their relations. Properly speaking, it is not a real analogy, but we can consider it as such in a loose or improper sense. A typical example one can use to illustrate the concept of this kind of analogy is the following: "Tom has the courage of a lion". Even in this case there is implicitly a kind of proportion: we can, in fact, reformulate this example in the following terms: . We see immediately that the quality "courageous" through which Tom can be likened to a lion is a quality which can be found in its highest degree in the lion: in a certain sense, this recalls the analogy of attribution. Nevertheless, there is a fundamental difference: there is no cause-effect relation between the courage of the lion and that of Tom, in that Tom is not courageous in virtue of a supposed participation in the courage of the lion. We cannot therefore speak of the analogy of proportion. It is instead a similarity which the knowing subject recognizes as an external observer between the courage of Tom and the courage of the lion. In this case, we have instead a similarity of relations between the subject and its quality, as in the case of the analogy of proportionality. Nevertheless, one cannot even speak of a true analogy of proper proportionality. In fact, in order to have an analogy of "proper" proportionality, the proportion that one wishes to establish would have to be: Tom is to the courage (of Tom) as the lion is to the courage (of the lion), whereas in the analogy of improper proportionality the same quality of courage proper to the lion (lion-like courage) is attributed to both Tom and the lion. Properly speaking, Tom has human courage, while the "lion-like courage" is attributed to him. We are dealing with a kind of "extrinsic" attribution, in that one attributes a character which is natural and proper to the lion to a natural endowment of Tom (cf. Thomas Aquinas, Summa Theologiae, I, q. 13, a. 3, 1um).

4. Analogia Entis. The fundamental discovery of the  metaphysics of antiquity has probably been that of the analogy of being (analogia entis). Unlike the different genera which, from the logical point of view, are formalized in "universal" concepts predicated in a univocal way of various subjects  as "man" is said with the same meaning of Tom, Dick, and Harry— "being" is predicated in an analogous way of several subjects and rises above the genera and universal concepts which describe them (cf. Aristotle, Metaphysics, 998b, 22-27).

We note here two relevant aspects of the issue: a) in particular, "being" is said of an object (substance) according to an analogy of proper proportionality of the object and its properties (accidents). This is a result of the fact that a property is always a property of something and can exist only in something else and not of its own accord. A color, a length, a temperature, etc. exist always and only in an object, while an object possesses an autonomous existence. Thus, one must say that a property is to its mode of being as an object is to its mode of being, but the two modes are not identical, though they may have in common the fact of being. b) In addition, "being" is said of a finite object, which has being by participation, and is said to be so according to an analogy of proportion with respect to the Pure Act which is being in itself and is the cause of the being of a finite object. A similar property to that of "being" is also characteristic of super-universal notions of "true", "one", and "good" which, together with "being", are called "transcendentals".

5. The Crisis of Analogy. The concept of analogy, which finds its most complete development and use in the philosophy of Thomas Aquinas, contains, beginning with Thomas Aquinas’ contemporaries, the seeds of its future downfall. In fact, from as early as the 13th century, the two great schools of philosophical-theological thought of Paris, where Albert the Great (1200 ca.-1280) and later his disciple Thomas Aquinas flowered, and of Oxford, the university of Roger Bacon (1214-1252), Robert Grosseteste (1174-1253) and later of John Duns Scotus (1275-1308) and William of Ockham (1280-1349), were in opposition and would follow two different paths without ever coming to a mutual understanding. The Aristotelian path of Albert the Great and Thomas Aquinas, was to be of great importance especially for Catholic theology and, three centuries later, would be officially recognized in large part by the Council of Trent (1545-1563). The Platonic path, prevalent in Oxford, would concentrate on the problem of the mathematical formulation of the sciences, beginning with Roger Bacon, creating the methodological premises for the development of modern science.

In this way, the gradual departure of an ever more univocal and mathematical scientific way of thinking from metaphysical and theological analogy-based thought, took root. Duns Scotus would resolve the analogy of being in a multiplicity of univocals just as William of Ockham would dissolve the reality of universals in a pure name (Nominalism) by denying to it a real existence outside of the mind. This development would then have an influence on the philosophical thought of  Descartes (1596-1650) and later of  Kant (1724-1805), with the success of Galileian and Newtonian science, and would eventually lead to the end of the very possibility of metaphysics as a science and consequently of theology as a systematic science. Nevertheless, for several decades, we have been witnessing a new turn in the sciences which seem to seek and in a certain sense discover anew the concept of analogy with the purpose of confronting new problems related to the theory of the logical and mathematical foundation of sciences and to the complexity of self-organizing structures. Even if it is too early to judge, one could say that the concept of analogy, which was initially excluded from scientific thought for fear of equivocity, now claims its place.

 

III. Analogy and Theology

The recourse to the concept of analogy in theology is necessary for many reasons. It cannot be otherwise since human reason, which is by its very nature creaturely, is able to approach the mystery of God only if it maintains the distance between creature and Creator by acknowledging that one can speak of God only by analogy and not in a univocal or equivocal way. In the context of the metaphysics of being, the analogia entis allows one to approach the problem of God’s existence as the basis of the being of all things and to predicate of God’s attributes and perfections starting from the way in which these perfections are participated in God’s works. But it is the very language of Revelation as presented in  Sacred Scripture which uses analogy in its various forms, be they proper or improper, as for example in the metaphor and even in the "parable", to express, through human concepts, that which would otherwise remain transcendent and ineffable in itself. The language of analogy is then used by theologians ( THEOLOGY) in their attempt to approach, through recourse to images and comparisons, the mysteries of faith, but also to see relations between such things, thereby grasping a deeper, inner coherence of God’s plan of salvation.

1. The Knowledge of God and Divine Names. The various applications of the concept of analogy to theology lie on different levels. The first question one asks concerns the knowledge of God, either through human reason alone ( GOD, IV.1) or by faith in what God revealed about Himself. Theologians have traditionally taken two paths to this aim: the first is the "apophatic" or "negative" way, typical of Eastern Christianity, which emphasizes the fact that we can only know with certainty what God is not, rather than what He is. Following this approach, such characteristics as composition, corporeality, finitude, and so on and so forth, are excluded from the notion of God. In addition to negative theology, and inspired by a scriptural passage from Book of Wisdom (cf. Wis 13,5) in which explicit reference to the concept of analogy is made ( WISDOM, BOOK OF of, III.3), Western Christianity also developed a positive theology. On the basis of the analogy of simple proportion, it allows one to recognize in God a similarity with the perfections found in creation, as effects whose summum analogatum is God Himself (cf. Thomas Aquinas, Summa Theologiae, I, q. 12). It involves a cognitive approach which certainly does not dissolve mystery in that, as the Fourth Lateran Council (1215) recalls, (DH 806).

Another classic theological problem which is closely tied to the problem of the knowledge of God, is that of the titles one can correctly attribute to God ("divine names"). This theme, already treated by pseudo-Dionysius in De Divinis Nominibus, was given a complete treatment by Thomas Aquinas who would let analogy play a decisive role. First of all, he maintained that the names which certainly denote what God is not (imperfections or ontological or moral limits) cannot be attributed to God. He then states that we can attribute to God the words we use to describe creatures, but only by analogy, as our language refers mainly to what we know of creatures. These are in fact an effect of which God is the cause, a cause which cannot be known directly by us. We cannot speak of Him univocally because God is a cause which is infinitely higher than His effects and transcends their nature as He does not belong to any genus. We cannot speak of Him equivocally, since there is a cause-effect relation, real from the creatures towards God, which distinguishes creatures from Him. Thus, the names signifying God’s perfections can be used by analogy of proportion, God being here the summum analogatum. When one says that something is good, one says so more properly of God, who is good in and of Himself, than of the creatures, who are good only by participation. Other names can be attributed to God only metaphorically. This happens either when one signifies a perfection by means of a name describing a creature who possesses it or when, instead of the name of a certain perfection, the creature’s name is attributed to God, having the intention of attributing to Him that perfection. This happens, for example, when in Holy Scripture God is called a "rock" or "lion", with the intention of attributing to Him the perfections of the rock and the lion (cf. Summa Theologiae, I, q. 13).

2. Examples of Analogy in the Scriptures. It is proper of the language of Holy Scripture to offer, through different literary genres, a great wealth of analogies and metaphors. This is due, as already mentioned above, to the need of expressing with human words used primarily to describe creatures, contents regarding the transcendent reality of God, which reason alone cannot reach and which is not an object of common experience. It is God who communicates His will and His plan through images based on analogy. It is asked of Abraham to try to conceive of the immense number of descendents of which he is called to be the father, by analogy with the great number of stars in the sky and grains of sand in the sea (cf. Gen 15,5 and 22,17). Another example is the prophet Jeremiah, who is invited by God to look at the renewal that God would bring about in the house of Israel (Jer 18, 1-4), by considering the analogy of the potter who forms and then destroys the work of his hands to make it new over again. The prophets themselves were the ones who spoke to the people through numerous images and analogies, drawing from what happens in nature, in their own history, and in the story of different peoples (Ez 31, 1-14; Hos 1,2-9; Dan 2,31-45).

Jesus would speak in "parables" rather frequently to describe with effective and coherent images, the reality of the Kingdom, in order to make it more understandable to his audience. The expression frequently recurs in the Gospels (cf. Mt 13,1-41; Mk 4,1-34; Lk 8,4-18). This comparison is based on the "analogy of proportionality". The use of images and metaphors establishes a simile between a known reality and one that it unknown or difficult to understand, favoring the transposition of properties and relations from the better known to the lesser known image. The parable is often told in the form of a story whose argumentative force consists in the narration of a fact (a fictitious but true-to-life fact) which the audience can understand well and through which the audience can draw the logical conclusions. Such conclusions, by dint of analogy, can be then applied in this case to the initially unknown reality so as to understand some of its most important characteristics. The language of the metaphor and parable, or if you prefer, of "narration", is particularly fitting to the human mind. We find ourselves in a situation in which it is possible to identify a series of unchanging relations between human beings and things, or between human beings themselves, beyond the changing objects of experience. These relations can be used as logical, cosmological, and anthropological coordinates to communicate a certain message. It is not surprising, however, that the Word of God, which has also taken on the history and logic of such a communicative and cognitive structure, taken together with the true humanity of Christ, has recourse to it as to a kind of "fundamental human language".

From an hermeneutic point of view the language of analogy in Scripture has a special role, that must be distinguished from the symbolic one, which is also present. In the case of analogy an analogate is always referred to, while symbolic language is intended to refer to a reality beyond the limits of human discourse and language, requiring completely new non-analogous categories. But symbol remains incomplete without the help of analogy, since it recalls a reality independent of symbol itself, with the risk of conceiving mentally an infinite chain of symbols never attaining its real object.

3. Uses of Analogy in Theology. Analogies are widely used in Ecclesiology when speaking of the Church, by resorting to "figures", as made for example by the Magisterium of the Second Vatican Council (cf. Lumen gentium, 6). The mystery of the Church, in fact, participates in the richness and transcendence of God, since she has her origin in the mystery of God the Father’s plan of salvation and is revealed and accomplished through the missions of the Son and the Holy Spirit. To be expressed by words, the reality of the Church needs the analogy of intrinsic and extrinsic proportionality. Based on Sacred Scripture and the teachings of the Fathers of the Church, theology employs different images for the Church: a flock led by the shepherd, the Lord’s vine, a house built on a keystone which is Christ, the Kingdom, the family and abode of God, and, above all, God’s people and the Body of Christ. It should be also observed that one must use this last analogy not in the metaphorical but in proper sense (cf. Lumen gentium, 7; Pius XII, Mystici corporis, 29.6.1943). The relationship between Christ and His Church is likened, in addition, to the relationship between the bride and the bridegroom, but also to the relationship of the head to its body. The peculiarity of such analogy-based images lies in the fact that none of them alone is adequate enough to express the mystery of the Church (due to her being both visible and invisible, temporal and eternal, one, yet present in many places; distinct from her Bridegroom, and yet one with her Head, etc.), whereas all of them together can play their part to clarify her character and properties.

Classic examples of applications of analogy can be found in the teaching concerning the sacraments: as stages of the "Christian life", they can be compared to the various phases of the "natural life", be it individual or social, according to an analogy of proper proportionality. In this way, Baptism is like "birth" to the Christian life, Confirmation is like "coming of age", the Eucharist is like nurturing oneself in one’s spiritual journey, and so on and so forth (cf. Thomas Aquinas, Summa Theologiae, III, q. 65). In the life of grace, then, sin is compared to death, so that one might understand its effects on the spiritual  soul, in analogy with what death brings about in the body. Even though such uses come with the limitations inherent in any type of comparison, they have undoubtedly aided our understanding of the mysteries of faith and facilitated its diffusion.

Concerning the relationship between scientific thought and religious faith, the theological analogies used throughout history to clarify the relationship between faith and reason (or between philosophy and theology), are worth noting. In medieval thought, philosophy is spoken of as the handmaiden of theology. Such a comparison, which has been frequently presented in a reductive and instrumental way, elicited Kant’s ironic response. Kant remarked that the handmaiden should have preceded her mistress, like a torch, in order to light the way. But the relationship between faith and reason has been viewed as a marriage relationship as well, a typical image also used to describe the relationship between nature and grace, stressing, however, the greater dignity of the faith-husband pole. Contemporary theology uses especially Marian and Christological analogies. Following the first analogy, faith-word-Spirit is accepted and embraced by reason-listening-Mary, thus "generating" the fruit of Theology, where theology is used here in the strong sense of a wisdom which participates, by dint of Revelation, in the uncreated Wisdom of Christ. In the Christological analogy, reason and faith are seen in relationship with one another as are human nature and divine nature in the Person of the Divine Logos made man ( JESUS CHRIST, INCARNATION AND DOCTRINE OF LOGOS). As Christ’s humanity gives visible and historical expression to the divine nature and person, so philosophy and reason give to theology and faith an indispensable language to express, in a clearly limited and incomplete, but authentic way, what one knows by faith, belonging to the transcendence of God.

Concerning the history of theology and its relationship with scientific thought, the essay of Joseph Butler (1692-1752) entitled The analogy of natural and revealed religion in the constitution and course of nature (1736) must be mentioned. In it, the author presents the course of nature and human history as a great analogy for the purpose of understanding the language and meaning of Christian revelation. The work would then become famous for its great influence on the thought of  John Henry Newman (1801-1890) who would often cite the work of this Anglican bishop in his books.

4. Analogia Fidei. A different meaning for the word analogy, at least when compared with its counterpart in Aristotelian-Thomistic philosophy, is that present in the expression "analogy of faith" (analogia fidei). It is first found in the letter of St. Paul to the Romans (, Rom 12,6), where the Greek term analoghía is used in the sense of "measure" or "proportion". In the Catholic tradition, this expression has taken on a technical character and signifies the inner coherence and harmony between the truths of faith which cannot contradict each other. The recent Catechism of the Catholic Church has defined it in the following way: (CCC 114). The analogy of faith guides us in our interpretation of the Old Testament in light of the New Testament. It is essential indeed for a correct understanding of what the "development of dogma" means. Under the guidance of analogy, such a development must not be viewed as a change of the content of truth, but as a consistent deepening of understanding of the same revealed truth. Classic sources for this understanding can be found in St. Vincent of Lerins (cf. Commonitorium, 53: PL 50, 668) and in John Henry Newman (cf. An Essay on the Development of Christian Doctrine, 1845).

Reformed theologians, especially Karl Barth (1886-1968), made use of the expression analogia fidei to indicate the one and only source of knowledge of God, that of divine Revelation, as opposed to analogia entis understood as the foundation of the path that allows natural reason to reach a non-revealed knowledge of God, a path which, in the Lutheran view, is denied at the root (LUTHER, MARTIN). Refusing the possibility of analogy-based knowledge of God arising from the experience of creatures, such theologians attempt to base the possibility and intelligibility of Revelation solely on the gift of grace. According to Karl Barth, . One might say of God only what God says of Himself, that is, his Word, Christ. It should be observed, however, that such a perspective does not seem to solve in a convincing way the problem of how to ground the intelligibility and understanding of the revealed word, in that, even though we are helped by grace, our understanding of God is always expressed through our own words, which are the only words we have at our disposal. "It remains true that the notions chosen by Christ to introduce us to the divine mystery are still human notions. Christ borrowed them from human language, from the whole range of created realities. And it is on the basis of these realities, objects of human experience, that is effected a purification and development of meaning which are dictated by the necessities of revelation [...]. If Christ can utilize all the resources of the created universe to make us know God and the ways to God, it is because the word of creation has preceded and left a foundation for the word of revelation; it is because both one and the other have their principle in the same interior Word of God. The revelation of Christ presupposes the truth of analogy" (R. Latourelle, Theology of Revelation, Alba House, New York 1966, pp. 366-367).

 

IV. Analogy and Science

Up to now, the concept of analogy has never been a part of any scientific theory even if it has always in fact accompanied the progress of science from the outside, suggesting new avenues of research and new interpretations of results. This can be understood by considering the fact that modern science, which employs the Galilean method, is as mathematical as possible. In mathematics, as it has been developed up to now, every symbol used in the same proof must unambiguously correspond to a single definition. In the second place, even when direct use of mathematics is not made, univocity is adopted so as to avoid the possibility of ambiguity or of error. It is however interesting to observe that in the last decades, research concerning the science of  complexity and self-reference in different fields seem to show the theoretical limits of univocity and to suggest an analogy-based approach.

1. Analogy alongside Scientific Theory: Analogy and Experimental Science. The word "analogy" is often used by scientists in their qualitative description of their results even if it has never been a part of any scientific theory. In particular, analogies have proven to be useful throughout the history of science and have been used for a two-fold purpose: (a) to suggest a way to build a theory (a heuristic purpose); (b) to aid in interpreting an already developed theory which is similar to another theory because it has a similar mathematical structure (a hermeneutic or interpretative purpose). In both cases, analogy, however, does not play a direct part in the mathematical formulation of the theory in that the symbols used continue to have an unambiguous definition. And it must be emphasized that from the Aristotelian-Thomistic point of view, we are dealing with "analogies of proper proportionality", that is, with similarities between relations. These similarities lie at the root of any possible model describing certain facts of experience. In particular, analogies, thus understood, can be said to be "material", i.e. concerning the "physical structure" of the systems to be described, or "formal", i.e. concerning the "mathematical laws" ( LAWS OF NATURE) which describe and explain determined behavior of physical systems.

"Material analogies" are useful in describing the properties of a system the internal structure of which is still unknown: one assumes that the unknown structure of the system may be similar to that of another well known system, governed by a known law. One says, in that case, that a "model" has been proposed to describe a system. A familiar example, in physics, is provided by the model of "elastic rigid balls", which is adopted as an approximated description of the behavior of gas molecules. In such a case the similarity between the model and the physical phenomenon is established on the level of the structure, of the material components; as a consequence a similar behavior of the two systems is also expected, and similar laws are supposed to govern them. It is the case of analogy of proper proportionality, which can be expressed by the following sentence: . A similarity between the relationships (balls-dynamics and molecules-dynamics) is established, which is so tight to legitimate the use of the same law to describe both systems within an acceptable error margin.

On the contrary, formal analogies are not based on a model of the physical constituents of a certain system, but on mathematical equations capable of describing its behavior without any hypothesis on the material structure governed by such laws (cf. Nagel, 1961). This way of proceeding is less natural to those who are not used to representing things in mathematical terms, whereas it is completely obvious to the mathematical physicist, used to substitute in his or her mind the physical object with the mathematical equations which govern its behavior. In certain cases, the formal equivalence of certain equations, which however have different physical interpretations of the same mathematical symbols, lead to new theories which are difficult to formulate without the aid of such a formal analogy. The most significant example of this can be found in wave mechanics ( QUANTUM MECHANICS, I-II): the Schrödinger equation, which is the fundamental equation of wave mechanics, is obtained through analogy with geometrical optics and classical, analytical mechanics ( MECHANICS, III).

But aside from the heuristic aspect of analogy in the sciences, there is also a hermeneutic aspect: analogy, in fact, can aid in the interpretation or explanation of the behavior of a certain system for which a certain model is adopted as it serves the purpose of reducing a lesser known phenomenon to a better known one. Suffice it to think of all of the microscopic models developed to explain the behavior of a macroscopic system: the kinetic theory, for example, gives, as a mechanical-statistical model of a thermodynamic macroscopic system, a detailed understanding of the macroscopic processes involving the variables which characterize the system. In this case, the analogy which one forms is the following: . If we accept this analogy and assume that it is possible to identify the laws of kinetic theory with those of thermodynamics within an acceptable margin of error, we can obtain a relationship between the kinetic theory quantities and those of thermodynamics and thereby obtain a kinetic interpretation of the latter: one may think, for example, of the conceptual identification of the absolute thermodynamic temperature with the average translational kinetic energy of the molecules in a gas. In this case, analogy proves to be advantageous since it leads to an increase in understanding.

2. Analogy alongside Scientific Theory: Analogy and Mathematical Science. If in physics, analogy does not play a direct role, except as a methodology suggesting from the outside how to build and interpret theories, formal analogy has a similar role in the development of new mathematical structures. The latter are intended to be based on simpler models for which one looks for a generalization which keeps some of their formal properties. It is important to keep in mind that in both physics and mathematics, analogy does not directly come into play as an "internal" element of the theoretical system, but plays a role in the building and interpretation of science. It is true that in the internal structure of mathematics there are biunivocal relations between elements of distinct sets (isomorphisms, homeomorphisms, diffeomorphisms, etc.), but we are not dealing, in this case, with real analogies of proper proportionality in the way it is understood above, but instead to structural equivalence. In these cases, there is a complete equivalence, and not only a similarity between the relations. For this reason, such sets are indistinguishable as far as the properties of the structure are concerned and one says that each of these sets is a "model" for the structure in consideration. In Aristotelian-Thomistic language, one could say that these models are like the "species" of the same "genus". A well-known example can be found in the so-called "Euclidean models" of non-Euclidean geometry and, more generally, in any mathematical model with an abstract structure. Non-Euclidean geometry, for example, can be thought of as abstractly defined by its axioms, regardless of the fact that there are different realizations of any one of its models. Nevertheless, as soon as we realize these models, they are not simply analogous but completely isomorphic to each other. It is so because every relation between the elements of the model corresponds to an equivalent and not only similar relation to the elements of the other model. In the example of non-Euclidean geometries, we can think of the hyperbolic geometry of Bolyai which can have as model the Euclidean model of Klein in the plane (cf. Courant and Robbins, 1996).

Another well-known example of two mathematical models with the same structure can be found in quantum mechanics which admits a two-fold representation in two isomorphic Hilbert spaces: that is, the Schrödinger picture, formulated in terms of wave-functions in an L2 Hilbert space (functions with a defined square modulus) and that of  Heisenberg, expressed in terms of l2 vectors expanded on an orthonormal basis of eigenfunctions (cf. Fano, 1971).

3. Analogy within Scientific Theories. The interest in analogy and the research devoted to the development of a "scientific theory of analogy" and a "method of demonstration" based on the latter, seems to emerge inevitably in the study of systems, be they biological, chemical, physical, mathematical, logical, or other, which are organized according to "hierarchical levels". Some of these levels cannot be reduced to more elementary ones (cf. Cini, 1994), because they differ not only "quantitatively" but "qualitatively". They have different natures but, at the same time, something real in common. In this case, it seems possible and useful to invoke the analogy of simple proportion or that of proper proportionality.

Up to now, sciences have involved the search for components which act as fundamental "parts" or "building blocks" to explain the structure of the universe as a "whole", assuming that the parts have the same nature as the whole (matter-radiation). In this scheme, the "building blocks" of the whole, according to the Standard Model, are "quarks" and "gluons" which bind them, which form particles once believed to be elementary, which in turn form nuclei and atoms, which then form molecules, and finally, living cells and more complex living organisms. Every level of this scale is considered perfectly homogeneous with the other levels, and is made of the same matter and considered of the same nature. In a sense which seems to contradict this way of framing the problem, qualitatively diversified (and hence irreducible to each other) levels have a tendency of emerging in the same system. If in fact one of these levels of organization (the "higher level") were in some way decomposable to other, more elementary ones (the "lower levels") and if it could be reconstructed through an appropriate recomposition of the latter, the higher level would not be "qualitatively" different, but a simple "superposition" of the lower levels. These do not represent absolutely disparate properties which cannot be compared to each other, but instead constitute, different ways of manifestation and realization of the same property, which can therefore be actuated not always in the same way (that is, not univocally), but according to differentiated ways which are really related to each other (that is analogically). In particular, we are faced with a two-fold modality in the relationship between the whole and its parts: on the one hand, we have a whole which is not reducible to the sum of the parts, but possesses a new informative and unifying element which characterizes it as a whole. On the other hand, we have parts in which there exists something similar to the whole. Such a structure is commonly described by scientists as "complex" (cf. Nicolis and Prigogine, 1989).

This situation is encountered in every contemporary scientific discipline: the irreducibility of the levels is none other than a sign of the insufficiency of reductionism in the formulation of scientific theories which deal with complex systems (cf. Dalla Porta Xydias, 1997). The biological sciences, for example, have always dealt with properties of living beings not shared by non-living beings, even from the chemical and physical point of view ( BIOLOGY). The behavior of a living being, even the simplest, cannot be described entirely by its constituent parts. On this level, the analysis of the constituent parts is no longer enough and a study of the new level of the whole is necessary. A thorough study of a somewhat complex molecule such as those found in a crystal lattice or a study of the impurities in a crystal which determine the electric properties of a semi-conductor (to cite a few examples) have shown that even in the chemistry of non-living objects the properties of the whole of a complex, composite structure cannot be deduced from the properties of the atoms comprising it ( CHEMISTRY, V). The existence of molecular orbitals of shared electrons cannot be thought of as electrons belonging to a single atom. In an electric conductor, the conduction electrons are in fact shared among all the atoms of the lattice. In the field of physics and mathematics, the problem of the whole and the parts is clearly of relevance in the two senses alluded to above: in particular, the "non-reducibility of the whole to the sum of the parts" is a consequence of the "non-linearity" of the differential equations which govern complex physical systems, whereas the self-replication of the whole in each of its parts is none other than a sign of "self-reference" which is of great relevance to the logician and to the computer scientist. In fact, it seems that computer scientists were the ones to revive the by now classical problems of mathematical logic. Take, for instance, the problems related to Godel’s theorem concerning the consistency and completeness of axiomatic systems or the problem of displaying sets, in all their  beauty, on the computer screen which up to then seemed to be "mathematical monsters" due to their infinitely winding boundary (as the Julia sets). One had to wait for the work of Benoit Mandelbrot to rekindle interest in these problems. The field of fractal geometry began to develop when the computer was utilized as a laboratory in which mathematical experiments could be performed, in a way similar to the manner in which Archimedes, more than two thousand years ago, performed mechanical experiments so as to catch a glimpse of geometrical properties; only later would he seek a logical demonstration of such properties beginning with a set of axioms. Research in the field of the so-called artificial intelligence, in addition, has afforded an understanding of the fact that information can be found on various levels and that there can be different hierarchies of  information: the lower level lies in the hardware of the machine, and the higher levels in the software; the programming language, in turn, contains the higher-level information related to the goal for which it was written (which lies in the mind of the programmer and in that of the user, and so on and so forth). In every scientific discipline, there seems to be a hierarchical structure of information related to the degree of complexity —and therefore of unity— of the structure studied. It therefore seems necessary to widen the scope of current scientific methodology and rationality so that the sciences can overcome the barriers erected by impossibility theorems such as that of Gödel (cf. De Giorgi et al., 1955).

The need for such a widening of scope is felt, first of all, in the study of "non-linearity". From the mathematical point of view, and therefore, from the point of view of all mathematical sciences, the impossibility of conceiving the whole as the sum of parts which are homogeneous with the whole (reductionism), is encountered in the field of non-linear differential equations for which, as it is well known, the sum of two or more solutions is not a solution, and conversely, every solution cannot be written as a linear combination of simpler solutions (which is the case with linear differential equations). Therefore, it is not possible to reduce the study of any given solution to simpler and already determined solutions in a non-linear system. Moreover, Nature itself is described almost completely by systems of non-linear equations and linear solutions are only a first approximation. Non-linearity, therefore, introduces the concept of the "irreducibility" of certain solutions to simpler ones. The different solutions, however, have something in common: they are all solutions of the same equation.

In the second place, the problem of self-reference must be considered. By "self-referring", a term originating in the field of logic, but which is now universally used, one means an operation or system whose "whole" is completely replicated, i.e., is completely identical to itself, in its parts. Self-reference had already been discovered by logicians of Ancient Greece who viewed it as a possible source of contradictions: one can think of the famous "liar’s paradox" in its different versions. For the same reason, modern logicians and mathematicians have carefully kept self-reference out of their axiomatic systems. Betrand Russell (1903) had excluded it from his set theory, where it had emerged (for example, in the idea of "self-inclusion" of certain sets of elements which contain themselves). Kurt Gödel (1931) had succeeded, on the contrary, in exploiting precisely the possibility of creating paradoxes through self-reference for the purpose of proving the undecidability of certain propositions of formal systems, such as the Principia Mathematica. He had deduced the incompleteness of such a system and the impossibility of demonstrating its consistency from within the system. The use of the computer, which makes ample use of recursive algorithms, brought up once again the problem of self-reference in the fields of logic and mathematics. If it is clear that self-reference can lead to contradictions, it is just as clear that this does not always and does not necessarily happen: we have a contradictory self-referring proposition when the predicate negates the truth of the proposition itself. For example: "this proposition is not true". In like manner, we have a contradiction in set theory when we restrict the set of all sets not to include itself: "the set of all sets that do not contain themselves" is contradictory because the definition restricts the set to contain itself and not to contain itself at the same time. Nevertheless, certain contradictions can be avoided if one has a clear idea as to how self-reference can be applied to "differentiated levels" of the same object, and if one understands that it must be interpreted in an analogous, and not univocal, sense. In this case, the "whole" cannot replicate into copies that are "identical to itself" but only "similar to itself".

4. The First Steps towards a Theory of Analogy. In this subsection, I shall give a few examples. The first example involves the acknowledgment of a hierarchy of levels. Where does the contradiction lie in the self-referential proposition, or in the definition of the ? The contradiction arises because the "proposition" () and the subject "this proposition" are identified with one another, whereas, in reality, they are not the same proposition. They have the fact of being propositions in common, but they differ in the "manner" they are propositions. Likewise, the is not a set in the same manner as the "sets which do not contain themselves". The fact of identifying them (univocity) does not take into account the difference in the mode of being of the sets and therefore gives rise to the contradiction. In order to eliminate this contradiction at its root, Russell proposed to classify the sets into "sets of differentiated types". Sets of simple elements (that is, elements which cannot be themselves sets) belong to the first level (or type), Sets whose elements can only be sets of the first type belong to the second level (or type). Sets of the third type are those whose elements are sets of the second type, and so on and so forth. In this manner, one obtains a hierarchy of sets belonging to different well-defined levels. Thus, the term "set" can be said in different senses depending on whether or not one is speaking of sets of the first, of the second, or of another level. A similar classification is made for propositions. To summarize, we can say that one has made the first small step towards the concept of analogy from a need arising from within the system. And this first step consists of introducing levels, or differentiated senses in which one can speak of the same term; thus the same object can be realized, as, in our case, a set or a proposition. It must be observed in point of this kind of analogy that it is possible to establish similarities between relations of different types of sets, in a way similar to what happens in the analogy of proper proportionality.

In connection with the subject of self-reference, another important direction can be found in the field of fractal geometry. Fractals are geometrical structures which have the noteworthy property of being "self-similar", that is, they replicate themselves infinitely in each of their parts. In certain cases, as the curve of von Koch, such self-similarity is so perfect that it is impossible to determine the scale of magnification of a given level, since the replicated form is always the same in every part (cf. Peilgen and Richter, 1986). In other cases, such as the Mandelbrot set, there is not a complete self-similarity, but an infinite replication of itself into "similar" copies which are not exactly the same as the whole. Unlike what happens with sets or propositions, each of the parts of a fractal which replicate the whole is not, however, identical to the whole. But, though being distinct from the whole, it is nevertheless similar in form to it. In this case, it is preferable to speak of "self-reference" instead of "self-referentiality". The latter geometrical example, even if it only gives a geometrical representation and is only an informal model, allows us to make a few considerations. (a) The geometrical structure is "similar" in its whole and in its parts, even if such a structure is actualized in slightly different ways in each part. Therefore, one cannot speak of complete identity, but only of similarity, as it so happens in the analogy of terms. (b) Every replicate is not properly speaking separable from the whole, but always subsists as a part of the primary whole. For this reason, the whole can be compared to a sort of "analogatum primum" (as in the "analogy of proportion"), on which every part physically depends. (c) One can establish relational correspondences between the parts and the whole, and the parts with each other, as in the "analogy of proportionality".

A further step can be made if we acknowledge the difference between "essence" and "existence". The decisive leap, which is needed for analogy in the strict sense, is to begin thinking of "objects" (as the scientist would say) or of "entities" (as the philosopher would say) which are "similar" but irreducible to the same "mode of existence". In order to characterize different "modes of existence", one needs to avoid reducing existence to a simple logical "non-contradiction", as is the tendency in formal logic. This kind of reduction makes the very notion of existence univocal, as it postulates that what is not contradictory, that is, what is thinkable, exists, and exists only because it is not contradictory and only according to a single mode determined by its non-contradictory nature. In philosophical language, this position is equivalent to that of "the identity of essence and existence". One can show that this kind of mathematical approach proves its own insufficiency using Gödel’s theorem. The first attempt to refute mathematical formalism through the distinction between existence and essence can be found in the intuitionist program (cf. Basti and Perrone, 1996). The intuitionist approach is pushed to the extreme position which denies the universal role of essence and overemphasizes that of existence. In fact, intuitionism posits the distinction between essence and existence by denying the "principle of excluded middle": in this way, proofs by contradiction are insufficient to prove the existence of a mathematical entity and are only capable of showing its logical impossibility. Existence must be proved with a constructive, finite method. Only what can be constructed with a finite number of operations exists: in other words, only this or that particular model can be constructed and therefore the universal cannot be reached and remains a pure name (Nominalism). It is interesting to observe how both formalism and intuitionism assume a univocist mind-set, whereas the analogy-based solution, which acknowledges differentiated modes of existence of the universal and the particular, seems to be more appropriate (cf. ibidem, pp. 220-223). Research in this direction is still in the development phase.

Another scientific field in which the concept of analogy is being used is that of  artificial intelligence, or better yet (and more generally), that of cognitive science, a wider field of study which involves not only problems dealing with machine learning but more generally problems in psychology, such as the mind-body relationship and the relationship between the mind and the brain in particular ( MIND-BODY, RELATIONSHIP). It is important to stress the effort made to overcome Cartesian dualism, a philosophical position according to which mind and body are two separate "objects" joined together in a completely extrinsic way (cf. Basti, 1991, p. 105). On the one hand, computer science has in practice forced us to revise such a dualistic-mechanistic view. In fact, information inserted in a machine by means of software and input peripherals, which allows the machine to interact with the external world, is not a "thing" to be placed on the same footing as the hardware, but lies on a higher plane. The stratification of different levels of information allows one to establish relationships between entities of different levels (which recalls the analogy of proportion) and relations between these relationships (which recall the analogy of proportionality). In this way, a structure of information emerges which is in a certain sense analogous. On the other hand, experimental study of the mind-body relationship of the human cognitive processes has by now convinced several scientists that the human mind works by analogy and not simply through an accumulation or extraction of information from a kind of data base (cf. Hofstadter et al., 1998). Consequently, with the intent of imitating human intelligence with a computer, one seeks a way of reproducing this kind of analogy-based operation and not simply a way of storing a lot of specific information concerning the problem which the machine is to solve according to a reductionist mind-set which isolates single parts of an object from all the rest. Certainly, it is not enough to found a theory on a merely intuitive notion of analogy taken from its everyday meaning in common language. A rigorous theory of analogy is therefore needed.

 

V. The "Profundity" of Analogy

In conclusion, the genius of analogy, for which scientific interest is gradually but slowly developing, lies in two fundamental aspects: (a) the fact that it distinguishes between qualitatively different, but really related, levels of the same entity; (b) the fact that it is inseparable from a true extra-mental reality that participates in the being. The Aristotelian-Thomistic concept of analogy, as we have striven to point out, acknowledges different hierarchic levels of being which differ by their very nature. For this reason, there are "things" and "principles" which allow these things "to be" and "to be what they are". The "principles" and "things" are irreducible to each other for the very reason that they have different natures. At the same time, they are not completely heterogeneous with one another since they constitute different modes of the same being they possess in a differentiated way. In Latin terminology, quod indicates the "thing" and quo the principles by which the thing "is" and "is what it is", that is, they possess their own characterizing properties. In the language of modern physics, we would say that that which is "observable" is a quod, whereas the quo is not only unobservable in practice, since it is in a certain sense confined in virtue of a certain infinite potential barrier (as a quark in an infinitely deep potential well), but it is not observable in theory, since it is of a completely different nature from the observable. For example, if the "thing" is a particle, its constitutive "principle" is not a particle, or at least not in the same but in an analogous way. For this reason, the "principle" is not observable. The unobservable quo is introduced not as a superfluous element of the theory (as if it were a hidden variable which could be eliminated), but as a simple principle which is in a certain sense necessary and inevitable to account for the observable phenomenon. It is clear that the mathematical sciences, in their current version, are not yet in the position to introduce into its language a quo which is irreducible by nature to a quantitative and relational quod. Nevertheless, in a "broad enough theory", such an introduction seems possible and plausible. In this way, one can widen a reductionist theory to a non-reductionist one which is able to accommodate principles which are irreducible and analogous to each other, without falling short, for this reason, of the rigorous demands of a formal theory.

The second characteristic which we cannot afford to ignore in the theory of analogy is its close link to logic and  truth, or in other words, the relationship between what is thought and extra-mental reality. Analogy can be fully understood only as a logical description of what is verified in the extra-mental reality of things, only if one can describe on the logical level what reality is on the ontological level. Consequently, a broad theory with which one can formalize analogy in the way it is understood here must be able to accommodate the distinction between both a purely logical-formal mode of existence (non-contradiction) and different real modes of existence (extra-mental) through the distinction between essence and existence.

Analogy is one of the tools which allow us to understand why essence and existence are not reducible to each other. In a certain way, it constitutes a response to the incompleteness of existential philosophy (the truth of the thing leads only to its emergence in the stream of existence and not to other questions) and of the essentialist philosophy (the truth of the thing consists only of the explanation of what it is, that is, its essence). Analogy also serves as a guide aiding us in the correct use of language and symbols as it prevents language from ending up in a continuous regress with no epistemological basis.

 

Alberto Strumia
(translated by Eric Chang)

 

See also: COMPLEXITY; LOGIC; MATHEMATICS, SAPIENTIAL VALUE OF; METAPHYSICS; REASON; SYMBOL; THEOLOGY.

 

Documents of the Catholic Church related to the subject:

 

Bibliography

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