4.

If you intend to say this, let me remind you that the mental act we call understanding is done by us in two ways: either by the mind and reason within itself, as when we understand that the intellect itself exists; or by occasion of suggestion from the senses, as in the case above mentioned, when we understand that matter exists. In the first of these two kinds of acts we understand through ourselves, i.e. by asking instruction of God concerning that which is within us; but in the second we understand by asking instruction of God regarding that of which intimation is given to us by the body and the senses. If these things be found true, no one can by his understanding discover whether that body of which you speak exists or not, but the person to whom his senses have given some intimation concerning it. If there be any living creature to which the senses give such intimation, since we at least see plainly that we are not among the number, I regard the conclusion established which I began to state a little ago, that the question [about the vehicle of the soul] is one which does not concern us. I wish you would consider this over and over again, and take care to let me know the product of your consideration.