CHAPTER IX.
The order of the present treatise requires, after these two parts of the Song have been discussed, according to my intention, that we now proceed to the third, in which I intend to purify the Song from a reproof which might be unfavourable to it.
And it is this, that before I composed it, this Lady seeming to me to be somewhat fierce and haughty against me, I made a little ballad, in which I called her proud and angry, which appears to be contrary to that which is here reasoned; and therefore I turn to the Song, and, under colour of teaching it how it is proper that it should excuse itself, I make an excuse for that which came before. And this, when one addresses inanimate things, is a figure which is called by rhetoricians, Prosopopoeia, and the Poets often use it. "My Song, it seems you speak this to oppose," The intention of which address, to make it more easy of understanding, it behoves me to divide into three sections: first, one affirms wherefore excuse is necessary; then, one proceeds with the excuse, when I say, "Though Heaven, you know;" finally, I speak to the Song as to a person well skilled in that which it is right to do when I say, "Be such excuse allowed."
I say, then, in the first place: "My Song, it seems you speak this to oppose The saying of a sister Song of mine." For the sake of similitude, I say sister; for as that woman is called a sister who is born of the same father, so may a man call that work a sister which is wrought by the same worker; for our work is in some degree a thing begotten. And I say why it seems opposed or contrary to that sister Song, saying: "This lovely Lady whom you count divine, Your sister called disdainful and morose." This accusation being affirmed, I proceed to the excuse, by quoting an example, wherein the Truth is quite opposite to the appearance of Truth, and it is quite possible to take the false semblance of Truth for Truth itself, regarding Truth itself as Falsehood. I say: "Though Heaven, you know, is ever high and pure, Men's eyes may fail, and find a star obscure;" where it is shown that it is the property of colour and light to be visible, as Aristotle affirms in the second book Of the Soul and in the book on Sense and Sensation. Other things, indeed, are visible, but it is not their property to be so, nor to be tangible, as in form, height, number, motion, and rest, which are said to be subject to the Common Sense, and which we comprehend by union of many senses; but of colour and light it is the property to be visible, because with the sight only we comprehend them. These visible things, both those of which it is the property and those subject to the Common Sense, inasmuch as they are visible, come within the eye; I do not say the things, but their form; through the transparent medium, not really, but by intention, as it were through transparent glass. And in the humour which is in the pupil of the eye this current which makes the form visible is completed, because that humour is closed behind like a mirror which has its glass backed with lead; so that it cannot pass farther on, but strikes there, after the manner of a ball, and stops; so that the form which does not appear in the transparent medium, having reached the disc behind, shines brightly thereon; and this is the reason why the image appears only in the glass which has lead at the back.
From this pupil the visual spirit, which is continued from it to the part of the Brain, the anterior, where the sensitive power is, suddenly, without loss of time, depicts it as in the clear spring of a fountain; and thus we see. Wherefore, in order that its vision be truthful, that is, such as the visible thing is in itself, the medium through which the form comes to the eye must be without any colour, and so also the humour of the pupil; otherwise the visible form would be stained of the colour of the medium and of that of the pupil. And this is the reason why they who wish to make things appear of a certain colour in a mirror interpose that colour between the glass and the lead, the glass being pressed over it.
Plato and other Philosophers said, indeed, that our sight was not because the visible came into the eye, but because the visual virtue went out to the visible form. And this opinion is confuted by the Philosopher in that book of his on Sense and Sensation. Having thus considered this law of vision, one can easily perceive how, although the star is always in one way bright, clear, and resplendent, and receives no change whatever except that of local movement, as is proved in that book on Heaven and the World, yet from many causes it may appear dim and obscure; since it may appear thus on account of the medium, the atmosphere, that changes continually. This medium changes from light to darkness, according to the presence or absence of the Sun; and during the presence of the Sun the medium, which is transparent, is so full of light that it overpowers the star, and therefore it no longer appears brilliant. This medium also changes from rare to dense, from dry to moist, because of the vapours of the Earth which rise continually. The medium, thus changed, changes by its density the image of the star, which passes through it, makes it appear dim, and by its moisture or dryness changes it in colour. In like manner it may thus appear through the visual organ, that is, the eye, which on account of some infirmity, or because of fatigue, is changed into some degree of dimness or into some degree of weakness. So it happens very often, owing to the membrane of the pupil becoming suffused with blood, on account of some corruption produced by weakness, that things all appear of a red colour; and therefore the star appears so coloured. And owing to the sight being weakened, there results in it some dispersion of the spirit, so that things do not appear united, but scattered, almost in the same way as our writing does on a wet piece of paper. And this is the reason why many persons, when they wish to read, remove the paper to some distance from the eyes, in order that the image thereof may come within the eye more easily and more subtly, and thereby the lettering is left impressed on the sight more distinctly and connectedly. For like reason the star also may appear blurred; and I had experience of this in the same year in which this Song was born, for, by trying the eyes very much in the labour of reading, the visual spirits were so weakened that the stars all appeared to me to be blurred by some white mist: and by means of long repose in shady and cool places, and by cooling the ball of the eye with spring water, I re-united the scattered powers, which I restored to their former good condition.
And thus, for the reasons mentioned above, there are many visible causes why the star can appear to us different to what it really is.