NOTE.--Mark, O reader, that if you know the nature of the soul and its properties, and if you have a correct notion of everything which concerns the soul, you will observe that most animals possess imagination. As to the higher class of animals, that is, those which have a heart, it is obvious that they have imagination. Man's distinction does not consist in the possession of imagination, and the action of imagination is not the same as the action of the intellect, but the reverse of it. For the intellect analyses and divides the component parts of things, it forms abstract ideas of them, represents them in their true form as well as in their causal relations, derives from one object a great many facts, which--for the intellect--totally differ from each other, just as two human individuals appear different to the imagination: it distinguishes that which is the property of the genus from that which is peculiar to the individual,--and no proof is correct, unless founded on the former; the intellect further determines whether certain qualities of a thing are essential or non-essential. Imagination has none of these functions. It only perceives the individual, the compound in that aggregate condition in which it presents itself to the senses; or it combines things which exist separately, joins some of them together, and represents them all as one body or as a force of the body. Hence it is that some imagine a man with a horse's head, with wings, etc. This is called a fiction, a phantasm; it is a thing to which nothing in the actual world corresponds. Nor can imagination in any way obtain a purely immaterial image of an object, however abstract the form of the image may be. Imagination yields therefore no test for the reality of a thing.
Hear what profit we derive from the preliminary disciplines, and how excellent the propositions are which we learn through them. Know that there are certain things, which would appear impossible, if tested by man's imagination, being as inconceivable as the co-existence of two opposite properties in one object: yet the existence of those same things, which cannot be represented by imagination, is nevertheless established by proof, and attested by their reality. E.g., Imagine a large globe, of any magnitude you like, even as large as the all-encompassing sphere: further an axis passing through the centre, and two persons standing on the two extremities of the axis in such a manner that their feet are in the same straight line with the axis, which may be either in the plane of the horizon or not: in the first case both persons would fall, in the second case one, namely the one who stands on the lower extremity would fall, the other would remain standing, as far as our imagination can perceive. It has however, already been proved that the earth has the form of a globe, that it is inhabited on both extremities of a certain diameter, that both the inhabitants have their heads towards the heaven, and their legs towards each other, and yet neither can possibly fall, nor can it be imagined; for it is incorrect to say that the one extremity is above, the other below; but the term "above" and "below" apply to both of them as regards their relative position to each other. Similarly it has been proved in the second chapter of the book on Conic Sections, that two lines, which at first are at a certain distance from each other, may approach each other in the same proportion as they are produced further, and yet would never meet, even if they were produced to infinity, although they are observed to be constantly converging. This is a fact which
