Mathematical Mirror

science, for art is concerned with the difficult and the good, as Aristotle says in Book 2 of the Ethics. If what is sought were easy, there would be no need to establish a science for it. Similarly, even if it is difficult, if it is not useful, there should be no science of it, because such labor would be foolish and empty. And unless it were very useful and contained many excellent truths, a separate science should not be established for it; rather, it suffices that it be determined in some partial book or chapter along with others in a common science. But among philosophers, a separate science is established for vision alone, such as Perspectiva the science of perspective/optics, and not for any other sense. Therefore, there must be a special utility in the wisdom gained through vision that is not found in the other senses. And what I have now touched upon in the Universal, I wish to exhibit in particular by returning to the roots of this most beautiful science. Indeed, some science may be greater, but none possesses such sweetness and beauty of utility.

C H A P T E R II.

SINCE, indeed, the optic nerves—that is, the concave ones that produce vision—arise from the brain, and since the authors of perspective attribute the judgments to be made concerning the twenty species of visible things (which will be touched upon later) to the distinctive virtue acting through vision, it is unknown whether that virtue of distance exists among the virtues of the soul whose organs are distinct in the brain. Many other things to be treated below suppose the certification of the virtues of the sensitive soul. Therefore, it is necessary to begin with the parts of the brain and the virtues of the soul so that we may find those things which are necessary for vision. The authors of perspective show us the way to this, revealing how visual nerves descend from the membranes of the brain and the skin of the skull, but no one explains all the things necessary in this part. I say, therefore, just as all natural philosophers and physicians agree on this matter,