FIRST ONE ASKS whether this book has animals for its subject.

1. It seems not, because every science has to do with things that are universal and incorruptible, but every animal is individual and corruptible, and therefore, etc.

2. Moreover, if it were about animals, then it would concern either some or all animals. But it is not more about some than others, and it would therefore be about them all. But this is impossible, since then it would seem to be infinite and the infinite cannot be known by humans.

3. Besides, an animal is composed of body and soul. Therefore any...

“CERTAIN MEMBERS of animals,” etc.¹ With respect to this second book, one asks whether the cause of similarity or dissimilarity among the members of various animals occurs as a result of the complexion of mixables or on account of the soul.²

1. It seems that this is not on account of the soul. This is because a cause of diverse things in a species produces a diverse effect in the species. But the souls of different animals differ in their species.³ Since, then, in the species their members are similar, that similarity cannot occur on account of the soul.

2. Likewise, the...

“WE HAVE ALREADY discussed the disposition of the members,”¹ etc. With respect to this third book we will first ask whether veins are necessary in an animal body.

1. It seems not. The natural power [vis naturalis] is in charge of providing nourishment for plants and in animals.² But there are no veins in plants delegated for nourishment. But a vein does not exist for another purpose, and therefore veins are not necessary.

2. Moreover, bones are nourished just like other members, but there are no veins in bones.³ It is therefore not necessary to posit the existence of veins in other...

“WE HAVE ALREADY said above,”¹ etc. With respect to this fourth book one may first ask about bloodless animals. And first, whether bloodless animals are naturally hot or cold.

1. And it seems that they are hot. This is because the container draws the content to its own complexion. But the sea is salty and, consequently, hot. Therefore, marine animals and those lacking blood are hot.

2. Moreover, flyers are hot and dry. But some bloodless animals are flyers, like bees and wasps. Therefore, such creatures are hot. Therefore, conversely, bloodless creatures will be naturally cold. The proof of the consequence...

“ABOVE WE DISCUSSED the disposition of all the members of animals,” etc.¹ In this fifth book one asks about generation, and first one asks about coition and propagation.² First, whether coition is necessary for the generation of an animal.

1. It seems not. The generative power is bestowed upon every animal so that the species, which cannot be preserved in the animal itself, may be preserved in one like itself. Therefore, since this power is given to every animal, the animal does not require anything beyond this in order to generate.

2. Moreover, every animal is corruptible. Therefore, it needs something in...

“IT IS NECESSARY that in addition to what we said, …” etc.¹ This sixth book is mainly concerned with egg-laying. And one asks first whether flyers naturally have to generate by laying eggs.

1. And it seems not. For subtle and light things are generated more quickly, and this is why males are formed in the uterus more quickly than are females. But flyers are subtler and lighter than walkers. Since, then, walkers generate without an egg acting as a medium, and since live young come forth from a womb, how much more so should this be the case in flyers?...

“THE NATURE AND generation of animals,” etc.¹ In this seventh book the Philosopher makes a determination concerning the disposition and behaviors of animals. One asks first in this seventh book why the Philosopher says in the text, “nature proceeds from the non-living to the living,”² and whether the non-living is naturally prior to the living.

1. It seems not. In the order of the universe there is one first [thing] which is prior by nature to that which is nearest to it. Thus the intelligences are naturally prior to the celestial bodies, and the celestial bodies are prior to those below...

“NOW THE TYPES of animal vary,” etc.¹ In this eighth book the Philosopher makes a determination regarding friendship or enmity among animals. This is why it is asked whether friendship and enmity are present in brute beasts.

1. It seems not. Those passions that surpass the sensible powers and operations are only present in those animals possessing a power that rises above sensation. But friendship and enmity surpass the sensible operations, and they are therefore not present in beasts.

2. Besides, friendship and enmity are not present in those whose operations are directed toward a single thing, because these exist with respect...

“A DISCUSSION, THEN, concerning the principle of human [generation],”¹ etc. In this ninth book one asks first, at what time human generation especially should take place.

1. And it seems that it should take place during adolescence, because generation ought to occur more or especially during a time when the material for generation is more abundant. But this material is moisture, and moisture is more abundant during adolescence. Therefore, etc.

2. In addition, heat is the effective principle of generation. But heat is more abundant during adolescence, which is clear from a human’s growth pattern. And this is why, etc.

3. Moreover, pleasure...

“PERHAPS IT HAPPENS to certain men,” etc.¹ Here a determination is made concerning an obstacle to generation. A question is first raised concerning this issue in the tenth book, namely, whether the mother or the father is more responsible for an obstacle to generation.

1. And it seems that it is the father. Because the more noble a thing is, the more things are necessary for its operation. But the male is nobler than the female, and therefore more things are required for its activity. But that which requires more things can also be impeded by more things; therefore, etc.

2. Moreover,...

“IN EVERY NOBLE opinion,” etc.² In this eleventh book one makes a determination regarding the scientific process. This is why in this eleventh book one inquires first whether there is a double mode of proceeding in science: one, descriptive,³ and the other by assigning causes.

1. And it seems not. Because a demonstration is a syllogism that creates knowledge [scire]. Since, therefore, every science creates knowledge, then every science will be capable of leading to demonstration, and as a result none will be descriptive.

2. In addition, “to know is to recognize a thing’s cause.”⁴ Whoever implants knowledge [scientia] implants knowledge [notitia]...

“WE HAVE ALREADY stated above that the members,” etc.¹ In his twelfth book the Philosopher establishes the composition of parts. Therefore, with respect to this, the twelfth book, we first inquire whether similar parts are immediately generated from the elements.

1. And it seems they are. This is because generation is analogous to decomposition [resolutio], although they differ either according to their causes or their ends, since that “which is first in generation is last in decomposition”² and contrariwise. But homogenous parts can be immediately decomposed into elements; therefore, they can also be immediately generated from them.

2. Besides, just as official...

“IT FOLLOWS NOW to speak about the nature of the teeth,” etc.¹ In this thirteenth book one should first inquire about the heart, because earlier there was an investigation into teeth and nails. And first one inquires into the complexion of the heart.²

1. And it seems that the heart is hot and moist. For the one generating and the one generated are alike. But the heart is the principle of the blood’s generation, and the blood is hot and moist. Therefore, the heart is hot and moist.

2. Moreover, like is nourished by one like itself. But the heart is nourished...

“THE DISPOSITION, then, follows in this manner,” etc.¹ Here the Philosopher makes a determination regarding the parts of bloodless animals. And this is why one inquires for the first time in Book Fourteen whether or not bile [fel] is only a superfluity.²

1. And it seems not. Because every member is generated from something like it, from which it is established in its complexion and essence. But there are many choleric members. Therefore, they are nourished by something choleric. But bile is such a thing, and therefore, etc.

2. Furthermore, everything that is produced as a result of nature operating in an...

“WE HAVE ALREADY determined above,” etc.¹ With regard to this fifteenth book, one first inquires into sex, and whether sex is necessary for the generation of animals.

1. And it seems not. For according to the Philosopher generation exists because the individual is corruptible.² Therefore, the generative power is implanted in it so that it can be preserved in species, although not in itself. Therefore, generation corresponds to corruption. But corruption can occur without any distinction of the sexes, and therefore so too can generation.

2. In addition, according to the Philosopher in the second book of On the Soul and the...

“NOW WE HAVE already declared that the powers,” etc.¹ About this sixteenth book he asks first whether the soul is in the sperm.

1. It seems that it is. For everything that has any consequent operations has a principle of these operations. But semen has operations, of which the soul is the principle, because it is nourished and grows and is moved, and these things are found only in animated things. Therefore, etc.

2. In addition, nothing acts except through that which is already in act. But the soul’s active power is in the semen, and generation is of like from like....

“WE HAVE ALREADY discussed the cause of sterility,” etc.¹ In this seventeenth book one inquires first whether there ought to be a distinction among the parts in birds’ eggs.

1. And it seems not, because there is a greater heat in birds’ eggs than in fish eggs; but there is greater heat in a woman than a bird. Therefore, since there is no distinction among parts in a woman’s seed [semen], a distinction will exist all the less in the seed of birds.

2. In addition, the middle savors the nature of the extremes. But in the first generation of the egg...

“WE HAVE ALREADY spoken above about the generation of animals,” etc.¹ One first inquires in this eighteenth book into the differentiation of the sexes. And first one asks whether the strength of the power causes the generation of a male.

1. And it seems not. Power proceeds in a radical way from the heart. For the power is stronger on the side to which the heart inclines more. But the heart’s location inclines to the left side; therefore, the power will be stronger there. If, then, the power’s strength were the cause of a male, a male would be generated more...

“CONSIDERATION MUST be given to the accidents by which [the members] are diversified,” etc. ¹ In this nineteenth book, first one inquires whether the embryo is nourished before its formation.

1. It seems not. For nothing is nourished unless it is alive. What is not alive in act, but solely in potency, is not nourished in act. But the embryo is like this before its formation.

2. In addition, the nutritive power has organs designated for it, but the embryo does not have organs before its formation. Therefore, etc.

3. In addition, the last nutriment or food of the members is blood, according...