On the doctrine that Dreams are sent from God, Books 1-2 (1.26-1.30)

Now what is my meaning in this statement? We know already that the body is divisible into three parts, and that it is capable of motion in six directions, inasmuch as it has three dimensions, in length, in depth, in breadth; and twice as many motions, namely six, the upward motion, the downward motion, that to the right, that to the left, the forward, and the backward motion. But, moreover, we are not ignorant that it is the vessel of the soul; and we are also aware that it is subject to the changes of being young, of decaying, of growing old, of dying, of undergoing dissolution.

And with respect to the outward senses, we are not, so far as that is concerned, utterly dull and mutilated, but we are able to say that that also is divided into five divisions, and that there are appropriate organs for the development of each sense formed by nature; for instance, the eyes for seeing, the ears for hearing, the nostrils for smelling, and the other organs for the exercise of the respective senses to which they are adapted, and also that we may call these outward senses messengers of the mind which inform it of colours, and

Again, the voice does not entirely escape our comprehension; but we know that one voice is shrill and another deep; that one is tuneful and harmonious, and another dissonant and very unmusical; and again, one voice is more powerful, and another less so. And they differ also in ten thousand other particulars, in kind, in complexion, in distance, in combined and separate tension of the tones, in the symphonies of fourths, of fifths, and of the diapason.

Moreover, there are some things which we know also with respect to that articulate voice which has been allotted to man alone of all animals, as, for instance, we know that it is emitted by the mind, that it receives its articulate distinctness in the mouth, that it is by the striking of the tongue that articulate utterance is impressed upon the tones of the voice, and which renders the uttered sound not only a bare, naked, useless noise, void of all characteristic, and that it discharges the office of a herald or interpreter towards the mind which suggests it.

Now then is the fourth element which exists within us, the dominant mind, comprehensible to us in the same manner as these other divisions? Certainly not; for what do we think it to be in its essence? Do we look upon it as spirit, or as blood, or, in short, as any bodily substance! But it is not a substance, but must be pronounced incorporeal. Is it then a limit, or a species, or a number, or a continued act, or a harmony, or any existing thing whatever?