Marsilio Ficino’s Platonic Theology, Volume II

7Truth, however, is not bodily; otherwise it would not be present in incorporeal things. Yet it is present in God, in angels, and in numbers, all of which are both incorporeal and true. And since incorporeal things are truer than bodies in proportion as they are purer and more stable, truth exists in them more fully than it does in bodies. More than this, truth does not properly exist in bodies at all. Bodies consist of two things, matter and form. Truth does not lie in matter, for through matter nothing truly belongs to any species of things: matter does not make anything truly a man, a horse, or any other determinate thing. Nor does truth lie in a bodily form, since no form whose power is tainted in matter is a true form. Mathematicians also bear witness to this, for they do not find true figures in bodies. A true circle placed upon a true plane would roll continually. Reason requires this, since such a circle touches the plane at one point, while a body cannot rest upon a point. No one has ever seen such things in bodies. True figures are therefore not present in bodies, perhaps because even the true principles of figures—at least so far as sense is concerned—are not present there: points, lines, and surfaces. Reason shows that a true point must lack length, a true line breadth, and a true surface depth. Nowhere in matter are such things found by sense. Since truth exists somewhere, yet is absent from bodies and sensation, it is without doubt in spirits. Truth is therefore incorporeal. The same conclusion is evident from this: truth resides most fully where knowledge resides. Knowledge is truly concerned with the universal principles of things, as when someone knows what goodness itself is or what justice is—the justice common to particular good and just actions and duties—and with similar things. Principles of this kind are incorporeal, since they are enclosed in no particular body but are common to many. The principle of body or circle is found whole in the smallest body or circle just as in the largest. The principle of length, breadth, or depth is entire in the smallest line, surface, or depth just as in the greatest. Finally, the principle of quantity itself corresponds as a whole to the entire quantity of any given thing. Therefore, the principles of body, figure, dimension, and even quantity itself are not bodily or extended; much less can other principles be bodily and extended. Moreover, the principles of things are immutable, for they cannot be otherwise, whereas all bodily things are mutable. Since knowledge is concerned with these principles, it is incorporeal; therefore truth too is incorporeal.