Chapter 1: Philosophical Writings

The Thomistic synthesis, prepared gradually by the saint's commentaries on Scripture, on Aristotle, on the Master of the Sentences, by the Summa contra Gentes, by the Disputed Questions, reached definite form in the Summa theologiae. We will speak first of his philosophical writings, then of his theological works.

Here come first the commentaries on Aristotle.

1. On interpretation (Peri hermenias, on the act of judgment).

2. The Later Analytics (a long study of method in finding definitions, of the nature and validity of demonstration).

3. The Physica (natural philosophy).

4. De coelo et mundo.

5. De anima.

6. The Metaphysica.

7. Ethical works.

In searching Aristotle the saint fastens attention, not so much on the last and highest conclusions concerning God and the soul, but rather on the first elements of philosophy, just as we go to Euclid for the axioms of geometry. Nevertheless Aquinas often finds that these elements are deepened and their formulation most exact when Aristotle transcends the contrary deviations, first of Parmenides and Heraclitus, secondly of Pythagorean idealism and atomistic materialism, thirdly of Platonism and Sophistry. In Aristotle the saint discovers what has justly been called the natural metaphysics of human intelligence, a metaphysics which, commencing from sense experience, rises progressively till it reaches God, the pure act, the understanding of understanding (Noesis noeseos).

In commenting on the Stagirite, St. Thomas discards Averroistic interpretations contrary to revealed dogma, on Providence, on creation, on the personal immortality of the human soul. Hence it can be said that he "baptizes" Aristotle's teaching, that is, he shows how the principles of Aristotle, understood as they can be and must be understood, are in harmony with revelation. Thus he builds, step by step, the foundations of a solid Christian philosophy.

In these commentaries St. Thomas also combats certain theses sustained by his Augustinian predecessors, but held by the saint to be irreconcilable with the most certain of Aristotle's principles. Aristotle conceives the human soul as the only substantial form of the human body. He maintains the natural unity of the human composite. Human intelligence, he maintains, is on the lowest rank of intelligences, and has as object the lowest of intelligible objects, namely, the intelligibility hidden in things subject to sense. Hence the human intelligence must use the sense world as a mirror if it would know God. And only by knowing the sense world, its proper object, can the human soul come, by analogy with that sense world, to know and define and characterize its own essence and faculties. Brief Analysis

At the court of Urban IV, St. Thomas had as companion William de Moerbecke, O. P.: who knew Greek perfectly. The saint persuaded William to translate from Greek into Latin the works of Aristotle. This faithful translator assisted the saint in commenting on Aristotle. Thus we understand why Aquinas has such a profound understanding of the Stagirite, an understanding far superior to that of Albert the Great. On many points of Aristotelian interpretation St. Thomas is the authentic exponent.

Here we proceed to underline the capital points of Aristotle's teaching, as presented by St. Thomas.

In the saint's commentaries we often meet the names of Aristotle's Greek commentators: Porphyry, Themistius, Simplicius, Alexander of Aphrodisia. He is likewise familiar with Judaeo-Arabian philosophy, discerning perfectly where it is true and where it is false. He seems to put Avicenna above Averroes.

In regard to form, as is observed by de Wulf, the saint substituted, in place of extended paraphrase, a critical procedure which analyzes the text. He divides and subdivides, in order to lay bare the essential structure, to draw out the principal assertions, to explain the minutest detail. Thus he appears to advantage when compared with most commentators, ancient or modern, since he never loses sight of the entire corpus of Aristotelian doctrine, and always emphasizes its generative principles. These commentaries, therefore, as many historians admit, are the most penetrating exposition ever made of Greek philosophy. Grabmann [16] notes that scholastic teachers [17] cited St. Thomas simply as "The Expositor." And modern historians [18] generally give high praise to the saint's methods of commentating.

Aquinas does not follow Aristotle blindly. He does point out errors, but his corrections, far from depreciating Aristotle's value, only serve to show more clearly what Aristotle has of truth, and to emphasize what the philosopher should have concluded from his own principles. Generally speaking, it is an easy task to see whether or not St. Thomas accepts what Aristotle's text says. And this task is very easy for the reader who is familiar with the personal works of the saint.

St. Thomas studied all Aristotle's works, though he did not write commentaries on all, and left unfinished some commentaries he had begun. On Interpretation From Aristotle's corpus of logic, called Organon, Thomas omitted the Categories, the Former Analytics, the Topics, and the Refutations. He explained the two chief parts.

1. De interpretatione (Peri hermenias) [19].

2. The Later Analytics [20].

In De interpretatione he gives us a most profound study of the three mental operations: concept, judgment, reasoning. The concept, he shows, surpasses immeasurably the sense image, because it contains the raison d'etre, the intelligible reality, which renders intelligible that which it represents. Then he proceeds to arrange concepts according to their universality, and shows their relation to objective reality. He finds that the verb "to be" is the root of all other judgments. We see that Aristotle's logic is intimately related to his metaphysics, to his teaching on objective reality, to his principle of act and potency. We have further a penetrating study of the elements in the proposition: noun, verb, and attribute. We see how truth is found formally, not in the concept, but in the objectively valid judgment. We are thus led to see ever more clearly how the object of intelligence differs from the object of sensation and imagination, how our intellect seizes, not mere sense phenomena, but the intelligible reality, which is expressed by the first and most universal of our concepts, and which is the soul of all our judgments, wherein the verb "to be" affirms the objective identity of predicate with subject.

The saint proceeds to justify Aristotle's classification of judgments. In quality, judgments are affirmative or negative or privative, and true or false. In modality they are possible or contingent or necessary. And at this point [21] enter problems on necessity, on contingency, on liberty. Finally we are shown the great value of judgments in mutual opposition, as contradictories, or contraries, and so on. We know how often this propositional opposition, studied by all logicians since Aristotle, is employed in the theology of Aquinas. Later Analytics [22] St. Thomas expounds and justifies the nature of demonstration. Starting with definition, demonstration leads us to know (scientifically) the characteristics of the thing defined, e. g.: the nature of the circle makes us see the properties of the circle. Then, further, we see that the principles on which demonstration rests must be necessarily true, that not everything can be demonstrated, that there are different kinds of demonstration, that there are sophisms to be avoided.

In the second chapter of this same work, he expounds at length the rules we must follow in establishing valid definitions. A definition cannot be proved since it is the source of demonstration. Hence methodical search for a real definition must start with a definition that is nominal or popular. Then the thing to be defined must be put into its most universal category, whence by division and subdivision we can compare the thing to be defined with other things like it or unlike it. St. Thomas in all his works follows his own rules faithfully. By these rules he defends, e. g.: the Aristotelian definitions of "soul," "knowledge," "virtue." Deep study of these commentaries on the Later Analytics is an indispensable prerequisite for an exact knowledge of the real bases of Thomism. The historians of logic, although they have nearly all recognized the great value of these Thomistic pages, have not always seen their relation to the rest of the saint's work, in which the principles here clarified are in constant operation. The Physica

Here the saint shows, in the first book, the necessity of distinguishing act from potency if we would explain "becoming," i. e.: change, motion. Motion we see at once is here conceived as a function, not of rest or repose (as by Descartes): but of being, reality, since that which is in motion, in the process of becoming, is tending toward being, toward actual reality.

Attentive study of the commentary on the first book of the Physica shows that the distinction of act from potency is not a mere hypothesis, however admirable and fruitful, nor a mere postulate arbitrarily laid down by the philosopher. Rather it is a distinction necessarily accepted by the mind that would reconcile Heraclitus with Parmenides. Heraclitus says: "All is becoming, nothing is, nothing is identified with itself." Hence he denied the principle of identity and the principle of contradiction. Parmenides, on the contrary, admitting the principle of identity and of contradiction, denied all objective becoming. St. Thomas shows that Aristotle found the only solution of the problem, that he made motion intelligible in terms of real being by his distinction of act from potency. What is in the process of becoming proceeds neither from nothingness nor from actual being, but from the still undetermined potency of being. The statue proceeds, not from the statue actually existing, but from the wood's capability to be hewn. Plant or animal proceeds from a germ. Knowledge proceeds from an intelligence that aspires to truth. This distinction of potency from act is necessary to render becoming intelligible as a function of being. The principle of identity is therefore, for Aristotle and Thomas, not a hypothesis or a postulate, but the objective foundation for demonstrative proofs of the existence of God, who is pure act.

From this division of being into potency and act arises the necessity of distinguishing four causes to explain becoming: matter, form, agent, and purpose. The saint formulates the correlative principles of efficient causality, of finality, of mutation, and shows the mutual relation of matter to form, of agent to purpose These principles thereafter come into play wherever the four causes are involved, that is, in the production of everything that has a beginning, whether in the corporeal order or in the spiritual.

Treating of finality, St. Thomas defines "chance." Chance is the accidental cause of something that happens as if it had been willed. The grave-digger accidentally finds a treasure. But the accidental cause necessarily presupposes a non-accidental cause, which produces its effect directly (a grave). Thus chance can never be the first cause of the world, since it presupposes two non-accidental causes, each of which tends to its own proper effect.

This study of the four causes leads to the definition of nature. Nature, in every being (stone, plant, animal, man): is the principle which directs to a determined end all the activities of the being. The concept of nature, applied analogically to God, reappears everywhere in theology, even in studying the essence of grace, and of the infused virtues. In his Summa the saint returns repeatedly to these chapters, [23] as to philosophical elements comparable to geometric elements in Euclid.

In the following books [24] Aquinas shows how the definition of motion is found in each species of motion: in local motion, in qualitative motion (intensity): in quantitative motion (augmentation, growth). He shows likewise that every continuum (extension, motion, time): though divisible to infinity, is not, as Zeno supposed, actually divided to infinity.

In the last books [25] Of the Physica we meet the two principles which prove the existence of God, the unchangeable first mover. The first of these principles run thus: Every motion presupposes a mover. The second thus: In a series of acting movers, necessarily subordinated, we cannot regress to infinity, but must come to a first. In a series of past movers accidentally subordinated an infinite regression would not be self-contradictory (in a supposed infinite series of past acts of generation in plants, say, or animals, or men). But for the motion here and now before us there must be an actually existing center of energy, a first mover, without which the motion in question would not exist. The ship is supported by the ocean, the ocean by the earth, the earth by the sun, but, in thus regressing, you are supposing a first, not an interminable infinity. And that first, being first, must be an unchangeable, immovable first mover, which owes its activity to itself alone, which must be its own activity, which must be pure act, because activity presupposes being, and self-activity presupposes self-being. De Coelo Et Mundo

St. Thomas commented further, on the two books of De generatione et corruptione. [26] Of the De meteoris [27] he explained the first two books. Of the De coelo et mundo, [28] the first three books.

Reading the work last mentioned, De coelo, [29] we see that Aristotle had already observed the acceleration of speed in a falling body and noted that its rate of speed grows in proportion to its nearness to the center of the earth. Of this law, later to be made more precise by Newton, St. Thomas gives the following foundation: The speed of a heavy body increases in proportion to its distance from the height whence it fell. [30].

In regard to astronomy, let the historians have the word. Monsignor Grabmann [31] and P. Duhem [32] give Aquinas the glory of having maintained, [33] speaking of the Ptolemaic system, that the hypotheses on which an astronomic system rests do not change into demonstrated truths by the mere fact that the consequences of those hypotheses are in accord with observed facts. [34]. De Anima

In psychology Aquinas expounds the three books of De anima, [35] the opusculum De sensu et sensato, [36] and the De memoria. [37].

In De anima, he examines the opinions of Aristotle's predecessors, particularly those of Empedocles, Democritus, and Plato. He insists on the unity of the soul in relation to its various functions. [38] Following Aristotle, he shows that the soul is the first principle of vegetative life, of sense life, of rational life, since all vital faculties arise from the one soul. [39].

How are these faculties to be defined? By the objects to which they are proportioned. [40] Having studied vegetative functions, he turns to sensation. Here we have penetrating analysis of the Aristotelian doctrine on characteristic sense objects (color, sound, and so on): and on sense objects per accidens (in a man, say, who is moving toward us). These sense objects per accidens (called in modern language "acquired perceptions") explain the so-called errors of sense. [41].

St. Thomas gives also [42] a profound explanation of this text from Aristotle: "As the action of the mover is received into the thing moved, so is the action of the sense object, of sound, for example, received into the sentient subject: this act belongs both to the thing sensed and to the thing sentient." St. Thomas explains as follows: Sonation and audition are both in the sentient subject, sonation as from the agent, audition as in the patient." [43].

Hence the saint, approving realism as does Aristotle, concludes that sensation, by its very nature, is a relation to objective reality, to its own proper sense object, and that, where there is no such sense object, sensation cannot exist. Hallucination indeed can exist where there is no sense object, but hallucination presupposes sensation. Echo, says Aristotle, presupposes an original sound, and even before Aristotle it had been observed that a man born blind never has visual hallucinations.

The commentary [44] insists at length that the thing which knows becomes, in some real sense, the object known, by the likeness thereof which it has received. Thus, when the soul knows necessary and universal principles, it becomes, in some real fashion, all intelligible reality. [45] This truth presupposes the immateriality of the intellective faculty. [46].

This same truth further presupposes the influence of the "agent intellect," [47] which, like an immaterial light, actualizes the intelligible object, contained potentially in sense objects, [48] and which imprints that object on our intelligence. That imprinting results in apprehension from which arises judgment and then reasoning. [49] The saint had already formulated the precise object [50] of human intelligence, namely, the intelligible being in sense objects. In the mirror of sense we know what is spiritual, namely, the soul itself, and God.

Just as intelligence, because it reaches the necessary and universal, is essentially distinct from sense, from sense memory, and from imagination, so too, the will (the rational appetite): since it is ruled only by unlimited universal good and is free in face of all limited, particular good, must likewise be distinct from sense appetite, from all passions, concupiscible or irascible. [51].

Immortality, a consequence of spirituality, immortality of the human intellect and the human soul, may seem doubtful in certain texts of Aristotle. [52] Other texts, more frequent, [53] affirm this immortality. These latter texts are decisive, if the agent intellect is, as St. Thomas understands, a faculty of the soul to which corresponds a proportionate intelligence which knows the necessary and universal, and hence is independent of space and time. These latter texts are further clarified by a text in the Nicomachean Ethics, [54] which seems to exclude all hesitation. Metaphysica

The saint's commentary on Aristotle's Metaphysica has three chief divisions:

1. Introduction to the Metaphysica. 2. Ontology. 3. Natural Theology. The Introduction Metaphysics is conceived as wisdom, science pre-eminent. Now science is the knowledge of things by their causes. Metaphysics, therefore, is the knowledge of all things by their supreme causes. After examining the views of Aristotle's predecessors, Thomas shows that it is possible to know things by their supreme causes, since in no kind of cause can the mind regress to infinity. The proper object of metaphysics is being as being. From this superior viewpoint metaphysics must again examine many problems already studied by the Physica from the viewpoint of becoming.

This introduction concludes with a defense, against the Sophists, of the objective validity of reason itself, and of reason's first principle, the principle of contradiction. [55] He who denies this principle affirms a self-destructive sentence. To deny this principle is to annihilate language, is to destroy all substance, all distinction between things, all truths, thoughts, and even opinions, all desires and acts. We could no longer distinguish even the degrees of error. We would destroy even the facts of motion and becoming, since there would be no distinction between the point of departure and the point of arrival. Further, motion could have none of the four causes as explanation. Motion would be a subject which becomes, without efficient cause, without purpose or nature. It would be attraction and repulsion, freezing and melting, both simultaneously.

A more profound defense of the objective validity of reason and reason's first law has never been written. Together with the saint's defense of the validity of sensation, it can be called Aristotle's metaphysical criticism, Aristotelian criteriology. "Criticism" is here employed, not in the Kantian sense of the word, but in its Greek root (krinein): which means "to judge" and the correlate noun derived from that verb (krisis) [56] Genuine criticism, then, is self-judgment, judgment reflecting on its own nature, in order to be sure it has attained its essential, natural object, namely, objective truth, to which it is naturally proportioned, as is the eye to color, the ear to sound, the foot to walking, and wings to flying. He who wishes to understand the saint's work De veritate must begin by absorbing his commentary on the fourth book of Aristotle's Metaphysica. Ontology

This name may be given to the saint's commentary on the fifth book. It begins with Aristotle's philosophic vocabulary. Guided by the concept of being as being, St. Thomas explains the principal terms, nearly all of them analogical, which philosophy employs. Here is a list of these terms: principle, cause, nature, necessity, contingence, unity (necessary or accidental): substance, identity, priority, potency, quality, relation, and so forth.

Further, he treats of being as being in the sense order, where he considers matter and form, not now in relation to becoming, but in the very being of bodies inanimate or animated. [57] Then he shows the full value of the distinction between potency and act in the order of being, affirming that, on all levels of being, potency is essentially proportioned to act; whence follows the very important conclusion: act is necessarily higher than the potency proportioned to that act. In other words, the imperfect is for the sake of the perfect as the seed for the plant. Further, the perfect cannot have the imperfect as sufficient cause. The imperfect may indeed be the material cause of the perfect, but this material cannot pass from potentiality to actuality unless there intervenes an anterior and superior actuality which acts for that superior end to which it is itself proportioned. Only the superior can explain the inferior, otherwise the more would come from the less, the more perfect from the less perfect, contrary to the principles of being, of efficient causality, of finality. Here lies the refutation of materialistic evolutionism, where each successive higher level of being remains without explanation, without cause, without reason. [58].

Book X treats of unity and identity. The principle of identity, which is the affirmative form of the principle of contradiction, is thus formulated: "That which is, is," or again: "Everything that is, is one and the same." From this principle there follows the contingence of everything that is composed, of everything that is capable of motion. Things that are composite presuppose a unifying cause, because elements in themselves diverse cannot unite without a cause which brings them together. Union has its cause in something more simple than itself: unity. Natural Theology The third part of Aristotle's Metaphysica can be called natural theology. St. Thomas comments on two books only, the eleventh and the twelfth, omitting the others which deal with Aristotle's predecessors.

The eleventh book is a recapitulation, dealing with the preliminaries for proving the existence of God. The twelfth book gives the actual proofs for the existence of God, of pure act. Since act is higher than potency, anything at all which passes from potency to act supposes, in last analysis, an uncaused cause, something that is simply act, with no admixture of potentiality, of imperfection. Hence God is "thought of thought," "understanding of understanding," not only independent, subsistent being, but likewise subsistent understanding, ipsum intelligere subsistens. Pure act, being the plenitude of being, is likewise the Supreme Good, which draws to itself all else. In this act of drawing, in this divine attraction, St. Thomas, in opposition to many historians, sees not merely a final cause, but also an efficient cause, because, since every cause acts for an end proportioned to itself, the supreme agent alone is proportioned to the supreme end. Subordination of agents corresponds to subordination of ends. Since the higher we rise, the more closely do agent and purpose approach, the two must finally be one. God, both as agent and as goal, draws all things to Himself. [59].

Let us note on this point the final words of St. Thomas. "This is the philosopher's conclusion: [60} There is one Prince of the universe, namely, He who is the first mover, the first intelligible, and the first good, He who above is called God, who is unto all ages the Blessed One. Amen."

But what he does not find in Aristotle is the explicit concept of creation from nothing, nor of eternal creation, and far less of free and non-eternal creation. Commentaries On The Ethics

St. Thomas comments on two works of Aristotle's ethical and moral treatises.

1. The Nichomachean Ethics. [61]. 2. The Politica. [62]. The Nicomachean Ethics Following Aristotle, the saint here shows that ethics is the science of the activity of the human person, a person who is free, master of his own act, but who, since he is a rational being, must act for a rational purpose, a purpose that is in itself good, whether delectable or useful, but higher than sense good. In this higher order of good man will find happiness, that is, the joy which follows normal and well-ordered activity, as youth is followed by its flowering. Man's conduct, therefore, must be in harmony with right reason. He must pursue good that is by nature good, rational good, and thus attain human perfection, wherein, as in the goal to which nature is proportioned, he will find happiness. [63].

By what road, by what means do we reach this goal, this human perfection? By the road of virtue. Virtue is the habit of acting freely in accord with right reason. This habit is acquired by repeated voluntary and well-ordered acts. It grows thus into a second nature which these acts make easy and connatural. [64].

Certain virtues have as goal the control of passions. Virtue does not eradicate these passions, but reduces them to a happy medium, between excess and defect. But this medium is at the same time the summit. Thus fortitude, for example, rises above both cowardice and rashness. Temperance, above intemperance and insensibility. [65].

Similarly, generosity holds the highway, between prodigality and avarice. Magnificence, between niggardliness and ostentation. Magnanimity, between pusillanimity and ambition. Meekness defends itself, without excessive violence, but also without feebleness. [66].

But disciplining the passions does not suffice. We must likewise regulate our relations with other persons by giving each his due. Here lies the object of justice. And justice has three fields of operation. Commutative justice acts in the world of material exchanges, where the norm is equality or equivalence. Above it lies distributive justice, which assigns offices, honors, rewards, not by equality, but by proportion, according to each man's fitness and merit. Highest of all is legal justice, which upholds the laws established for the well-being of society. Finally we have equity, which softens the rigor of the law, when, under the circumstances, that rigor would be excessive. [67].

These moral virtues must be guided by wisdom and prudence. Wisdom is concerned with the final purpose of life, that is, the attainment of human perfection. Prudence deals with the means to that end. It is prudence which finds the golden middle way for the moral virtues. [68].

Under given circumstances, when, for instance, our fatherland is in danger, virtue must be heroic. [69].

Justice, indispensable for social life, needs the complement which we call friendship. Now there are three kinds of friendship. There is, first, pleasant friendship, to be found in youthful associations devoted to sport and pleasure. There is, secondly, advantageous friendship, as among businessmen with common interests. Finally there is virtuous friendship, uniting those, for example, who are concerned with public order and the needs of their neighbor. This last kind of friendship, rising above pleasure and interest, presupposes virtue, perseveres like virtue, makes its devotees more virtuous. It means an ever active good will and good deed, which maintains peace and harmony amid division and partisanship. [70].

By the practice of these virtues man can reach a perfection still higher, namely, that of the contemplative life, which gives genuine happiness. Joy, in truth, is the normal flowering of well-ordered activity. Hence the deepest joy arises from the activity of man's highest power, namely, his mind, when that power is occupied in contemplating its highest object, which is God, the Supreme Truth, the Supreme Intelligible. [71].

Here we find those words of Aristotle which seem to affirm most strongly the personal immortality of the soul. St. Thomas is pleased to underline their importance. Aristotle's words on contemplation run as follows: "It will in truth, if it is lifelong, constitute perfect happiness. But such an existence might seem too high for human condition. For then man lives no longer as mere man, but only is as far as he possesses some divine character. As high as this principle is above the composite to which it is united, so high is the act of this principle above every other act. Now if the spirit, in relation to man, is something divine, divine likewise is such a life. Hence we must not believe those who counsel man to care only for human affairs and, under pretext that man is mortal, advise him to renounce what is immortal. On the contrary, man must immortalize himself, by striving with all his might to live according to what is most excellent in himself. This principle is higher than all the rest. It is the spirit which makes man essentially man."

Many historians have noted, as did St. Thomas, that in this text the Greek [72] word for mind signifies a human faculty, a part of the soul, a likeness which is participated indeed from the divine intelligence, but which is a part of man's nature. Man it is whom Aristotle counsels to give himself to contemplation, thus to immortalize himself as far as possible. He goes so far as to say that this mind [73] constitutes each of us.

This summary may let us see why St. Thomas made such wide use of these ethical doctrines in theology. They serve him in explaining why acquired virtue is inferior to infused virtue. They serve likewise to explore the nature of charity, which is supernatural friendship, uniting the just man to God, and all God's children to one another. [74]. The Politica

St. Thomas commented the first two books, and the first six chapters of the third book. What follows in the printed commentary comes from Peter of Auvergne. [75].

We note at once how Aristotle differs from Plato. Plato, constructing a priori his ideal Republic, conceives the state as a being whose elements are the citizens and whose organs are the classes. To eliminate egoism, Plato suppresses family and property. Aristotle on the contrary, based on observation and experience, starts from the study of the family, the first human community. The father, who rules the family, must deal, in one fashion with his wife, in another with his children, in still another with his slaves. He remarks that affection is possible only between determinate individuals. Hence, if the family were destroyed there would be no one to take care of children, who, since they would belong to everybody, would belong to nobody, just as, where property is held in common, everyone finds that he himself works too much and others too little.

Aristotle, presupposing that private ownership is a right, finds legitimate titles to property in traditional occupation, in conquest, in labor. He also holds that man is by his nature destined to live in society, since he has need of his fellow men for defense, for full use of exterior goods, for acquiring even elementary knowledge. Language itself shows that man is destined for society. Hence families unite to form the political unity of the city, which has for its purpose a good common to all, a good that is not merely useful and pleasurable, but is in itself good, since it is a good characteristic of rational beings, a good based on justice and equity, virtues that are indispensable in social life.

These are the principal ideas proposed by Aristotle in the first books of the Politica, and deeply expounded by St. Thomas. In the Summa [76] he modifies Aristotle's view of slavery. Still, he says, the man who cannot provide for himself should work for, and be directed by, one wiser than himself.

In the second book of the Politica we study the constitutions of the various Greek states. Thomas accepts Aristotle's inductive bases, and will employ them in his work De regimine principum. [77] In the nature of man he finds the origin and the necessity of a social authority, represented in varying degree by the father in the family, by the leader in the community, by the sovereign in the kingdom.

He distinguishes, further, good government from bad. Good government has three forms: monarchical, where one alone rules, aristocratic, where several rule, democratic, where the rule is by representatives elected by the multitude. But each of these forms may degenerate: monarchy into tyranny, aristocracy into oligarchy, democracy into mob-rule The best form of government he finds in monarchy, but, to exclude tyranny, he commends a mixed constitution, which provides, at the monarch's side, aristocratic and democratic elements in the administration of public affairs. [78] Yet, he adds, if monarchy in fact degenerates into tyranny, the tyranny, to avoid greater evils, should be patiently tolerated. If, however, tyranny becomes unbearable, the people may intervene, particularly in an elective monarchy. It is wrong to kill the tyrant. [79] He must be left to the judgment of God, who, with infinite wisdom, rewards or punishes all rulers of men.

On the evils of election by a degenerate people, where demagogues obtain the suffrages, he remarks, citing St. Augustine, that the elective power should, if it be possible, be taken from the multitude and restored to those who are good. St. Augustine's words run thus: "If a people gradually becomes depraved, if it sells its votes, if it hands over the government to wicked and criminal men, then that power of conferring honors is rightly taken from such a people and restored to those few who are good." [80].

St. Thomas commented [81] also the book De causis. This book had been attributed to Aristotle, but the saint shows that its origin is neo-Platonic. He likewise expounded [82] a work by Boethius: De hebdomadibus. His commentary on Plato's Timaeus has not been preserved.

All these commentaries served as broad and deep preparation for the saint's own personal synthesis. In that synthesis he reviews, under the double light of revelation and reason, all these materials he had so patiently analyzed. The synthesis is characterized by a grasp higher and more universal of the principles which govern his commentaries, by a more penetrating insight into the distinction between potency and act, into the superiority of act, into the primacy of God, the pure act.

The saint knew and employed some of Plato's dialogues: Timaeus, Menon, Phaedrus. He also knew Plato as transmitted by Aristotle. And St. Augustine passed on to him the better portion of Plato's teaching on God and the human soul. Neo-Platonism reached him first by way of the book De causis, attributed to Proclus, and secondly by the writings of pseudo-Dionysius, which he also commented.

Among the special philosophic books which the saint wrote, we must mention four: De unitate intellectus (against the Averroists): De substantiis separatis, De ente et essentia, De regimine principum.