"The mind dwells on a mixture of whatever nature endows with imitable form, including things which may never have been perceived externally. But although the mind is present in everything, the origin of images is not in the mind. This is nothing to be surprised at, given that (despite our best efforts) we are not cognizant of our bodily expression and complexion before, in the throes of joy, displeasure and other such movements of the soul, we set their images in our faces. What is worthy of your surprise and contemplation is the way expressions are made to follow affections by the action of hidden numbers in the soul, independent of any drummed-up image of a bodily form. From this I hope that, when you perceive how many of the soul's movements are free of those images into which you are now inquiring, you will understand that the least likely movement by which [true knowledge of] a given body may come to the mind is meditation on sensible forms, which I do not believe the mind can experience without using the body and its senses."
Letter 7 (to Nebridius):4, 7, ca. 387/8.