No intellectual function is found in the life of brute animals, which can be concretely enumerated as follows.⁴⁰ The ability to form universal concepts from material things that are perceived by the senses. The ability to form concepts of supra-sensible things. The ability to perceive multiple relations formally as such. The ability to elicit formal judgments. The ability to form logical reasoning processes.⁴¹ The ability to know oneself and one’s acts by formal reflection, and to be able to attribute these formally to oneself. However, since these functions can differ between various persons, the argument for the superiority of mankind can be restricted to the two more principle intellectual functions of man, which are the universal concept and the concept of relationship.

Therefore, animals lack an intellect, as is evident from the positive nature of self activity in complex operations, and from the defect in animals of multiple perfections which naturally flow from the intellect. Consider each:

Considering the positive nature of self activity⁴² even in the most perfect operation of animals: First, in the most complicated and most marvelous activity, animals act from the impulse of nature,⁴³ instinct, otherwise their superior activity would exceed that of the human intellect; what proves too much, proves nothing (quod nimis probat, nihil probat). Second, animals lack a universal idea of perfecting their work, and are led only by concrete images; otherwise they would act in multiple and varied ways, such as man, with a universal idea of house, builds diverse houses. Third, animals do not perceive formal relations, such as between cause and effect, such as the dog taking meat in a friendly way from the thief. Fourth, animals do not perceive the most obvious relation, between means and end, even when the finality of marvelous operations is lost, such as the captive beaver building a dam, or the bees who prepare the cells of the queen, even though they lack a queen.

Concerning the defect in animals of multiple perfections⁴⁴ which naturally flow from the intellect: First, animals have a lack of conceptual speech which naturally flows from the intellect and without which there is no utility and joy of sharing thoughts and desires; while all men use conceptual languages, and no one denies that animal are incapable of conventional language.⁴⁵ Animals do make sounds of warning, fear, attack, but these are only called language by analogy, interpreted anthropomorphically. Second, animals have a defect of perfectability and progress.⁴⁶ What some wish to call progress in animals does not exceed the sensitive and instinctive order.⁴⁷

Therefore, animals do lack intellect,⁴⁸ since there is no sign of intellectual function in animals, neither from positive marvelous activity, nor from defect of perfection. The lack of an intellect is an essential discontinuity between animals and man.

Further proof that man is essentially different from the other animals is that intellectual cognition in man is irreducible to sensitive cognition.⁴⁹

Proof exists that cognition in man is irreducible to sensitive cognition.⁵⁰ Intentional objects which a rational man perceives in his intellection, looking within himself, appear rather diverse from sensitive objects he perceives or his imagination reproduces, and not just diverse from sense objects but irreducible to these sense objects. Such intentional objects are objects of universal concepts by which any human sensitive perception is intrinsically completed. There are other intentional objects which are immaterial, so that they would have no material properties, such as volume, extention, or location in space. Therefore, cognitions which as intellections are experienced by everyone are diverse from sensitive congnition or reproduction by imagination, and are irreducible to these objects. Therefore, if the intellective cognition of man is irreducible to sensitive cognition, then there is an essential discontinuity between man and the other animals.