Does St. Thomas teach about the nature of animals? Yes, following the teaching of Aristotle, St. Thomas assigns one type of soul to animals, the sensitive soul. St. Thomas says, "The animal is characterized by sense, that is to say from the sensitive soul, as from its essential form" (Aquinas Summa Theologiae Supplementum 79. 2. ad 3).³⁰

How does St. Thomas divide the animal kingdom? For St. Thomas, the great division is between man and the other animals. St. Thomas bases this division on the vital principle of animals, which is totally material like the rest of creation, except for man. St. Thomas maintains: "The brute animals, plants, minerals and all mixed bodies are corruptible, either totally or partially, sometimes due to the material which loses it form, at other times due to the form not remaining in act. Therefore such beings do not have a necessary relation to incorruptibility. So in the final renewal these (animals and material creatures) will not remain, but only incorruptible creatures" (Aquinas Summa Theologiae Supplementum 91. 5).³¹

Does the intellect of man depend on the senses? Yes, St. Thomas and all the Scholastics maintain that "There is nothing in the intellect which is not first in some way in the senses."³² Therefore man is like the animals in that man has extrinsic dependence of the intellect on the senses. St. Thomas maintains: "It is the property of the human intellect to know the forms that have an individual subsistence in material, but not in so far as they are in determined material. Now, to know what exists in a determined material, not as it is found in that material, means to abstract the individual form represented by the phantasm from the material. Thus it is necessary to conclude that our intellect knows material things by abstraction from phantasms, and that from such a knowledge of material things we are able to come to a certain knowledge of immaterial things" (Aquinas Summa Theologiae 1. 85. 1).³³

Does St. Thomas teach that animals have a sense appetite associated with instinct? Yes, St. Thomas affirms instinct in animals, by noting: "The animals have a natural instinct, inserted in them by divine reason, through which the animals exercise external and internal movements similar to the movements from reason" (Aquinas Summa Theologiae 2-2. 46. 4. ad 2).³⁴

Does instinct more or less determine animals to act in a certain uniform way, so that this observation allows St. Thomas to deny that sense and intellect are the same? Yes, according to St. Thomas, animals are moved by their very nature to determined acts: "Sense is found in all animals. But animals other than man do not have intellect. This is clear because animals do not operate in diverse and opposite ways (from their nature) as if they had an intellect; but animals are moved by nature toward certain determined and uniform operations in the same species, so that every swallow builds a nest in the same way. Therefore the intellect and sense are not the same" (Aquinas Summa Contra Gentiles 2. 66).³⁵

If man has some operations similar to plants and beasts, why would St. Thomas think that man is different? St. Thomas answers that some activities of man are under the control of man: "A human act is not any act by a man or in a man, because in some acts man operates like plants or beasts, even if the act is proper to man. Now with respect to other things, man alone has this property, to be the ruler of his own acts (sui actus est dominus), so whatever act of which man is the ruler, is properly a human act" (Aquinas De Virtutibus in Communi 1. 4).³⁶

Does St. Thomas also make an essential distinction between sense and intellect? St. Thomas answers that the essential distinction between man and animals is that animals only know the singular by way of sense, while man can know the universal by intellect. St. Thomas notes: "Only rational created nature has an immediate relation to God: because other creatures do not attain to the universal, but only to the particular, either by participating in divine goodness by just existing, just as inanimate things, or else by living and knowing singulars, just as plants and animals. Rational nature, as far as it knows the universal nature of the good and of being, has an immediate order to the universal principle of being" (Aquinas Summa Theologiae 2-2. 11. ad 3).³⁷

Does St. Thomas treat language? No, St. Thomas does not treat language directly and systematically.³⁸ However, St. Thomas has taken some positions with regard to language. The theological significance of language is to speak to God (Aquinas Scriptum in Liber Sententiarum 1. 22. 1. expositio textus). Concerning the Biblical senses of language, St. Thomas gives primacy to the literal sense, but admits some allegorical interpretation (Confer: Aquinas Summa Theologiae 1. 1. 10. ad 1). Concerning the pedagogical function of language, St. Thomas notes: "The teacher proposes to the disciple the signs of intelligible thing from which the agent intellect collects intelligible forms, and impresses them on the possible intellect. These same words of the master, heard or read, have the same effect, in causing knowledge in the intellect of things external to the soul, because the intellect takes from both (thing and word) by intelligible forms, although the words of the master have more immediate effect in causing knowledge than the sensible object existing outside the soul, because (words) are signs of intelligible forms" (Aquinas De Veritate 11, 1. ad 11).³⁹