This we cannot deny. If we say that these are effects of powers which animals also have, and of the powers of the bodily senses, we see clearly and evidently that the animals are, in regard to these powers, superior to man. For example, the sight of animals is much more keen than the sight of man; so also is their power of smell and taste. Briefly, in the powers which animals and men have in common, the animal is often the more powerful. For example, let us take the power of memory. If you carry a pigeon from here to a distant country, and there set it free, it will return, for it remembers the way. Take a dog from here to the center of Asia, set him free, and he will come back here and never once lose the road. So it is with the other powers such as hearing, sight, smell, taste and touch.
Thus it is clear that if there were not in man a power different from any of those of the animals, the latter would be superior to man in inventions and the comprehension of realities. Therefore, it is evident that man has a gift which the animal does not possess. Now, the animal perceives sensible things but does not perceive intellectual realities. For example, that which is within the range of its vision the animal sees, but that which is beyond the range of sight it is not possible for it to perceive, and it cannot imagine it. So it is not possible for the animal to understand that the earth has the form of a globe. But man from known things proves unknown things and discovers unknown truths. For example, man sees the curve of the horizon, and from this he infers the roundness of the earth. The Pole Star at Akká, for instance, is at 33—that is to say, it is 33 above the horizon. When a man goes toward the North Pole, the Pole Star rises one degree above the horizon for each degree of distance that he travels—that is to say, the altitude of the Pole Star will be 34, then 40, then 50, then 60, then 70. If he reaches the North Pole the altitude of the Pole Star will be 90 or have attained the zenith—that is to say, will be directly overhead. This Pole Star and its ascension are sensible things. The further one goes toward the Pole, the higher the Pole Star rises; from these two known truths an unknown thing has been discovered—that is, that the horizon is curved, meaning that the horizon of each degree of the earth is a different horizon from that of another degree. Man perceives this and proves from it an invisible thing which is the roundness of the earth. This it is impossible for the animal to perceive. In the same way, it cannot understand that the sun is the center and that the earth revolves around it. The animal is the captive of the senses and bound by them; all that is beyond the senses, the things that they do not control, the animal can never understand, although in the outer senses it is greater than man. Hence it is proved and verified that in man there is a power of discovery by which he is distinguished from the animals, and this is the spirit of man.