Leonardo on perspective

What qualities does Leonardo claim for his own art in contrast to that of others? Why does he feel that perspective is important?

Introduction

Because I can find no useful or pleasant subject to discourse on, since the men who came before me have taken all the useful and pleasant subjects and discoursed on them at length, I find I must behave like a pauper who comes to the fair last, and can provide for himself in no other way than to take those things of trivial value that have been rejected by other buyers. I, then, will fill my shopping bag with all these despised and rejected wares, trash passed over by previous buyers, and take them and distribute them, not in the great cities, but in the poorest villages, taking whatever money might be offered.

I realize many will call my little work useless; these people, as far as I'm concerned, are like those whom Demetrius was talking about when he said that he cared no more for the wind that issued from their mouths than the wind that issued from their lower extremities. These men desire only material wealth and are utterly lacking in wisdom, which is the only true food and wealth for the mind. The soul is so much greater than the body, its possessions so much nobler than those of the body. So, whenever a person of this sort picks up any of my works to read, I half expect him to put it to his nose the way a monkey does, or ask me if it's good to eat.

I also realize that I am not a literary man, and that certain people who know too much that is good for them will blame me, saying that I'm not a man of letters. Fools! Dolts! I may refute them the way Marius did to the Roman patricians when he said that some who adorn themselves with other people's labor won't allow me to do my own labor. These folks will say that since I have no skill at literature, I will not be able to decorously express what I'm talking about. What they don't know is that the subjects I am dealing with are to be dealt with by experience (1) rather than by words, and experience is the muse of all who write well. And so, as my muse, I will cite her in every case.

Although, unlike my critics, I am not able to facilely quote other writers, I will rely on an authority much greater and much more noble: on Experience, the Mistress of their Masters. These fellows waddle about puffed up and pretentious, all dressed up in the fruits, not of their own labors, but of other people's labors; these fellows will not allow me my own labors. They will scorn me as an inventor and a discoverer, but they should be blamed more, since they have invented and discovered nothing but rather go about holding forth and declaiming the ideas and works of others.

There are men who are discoverers and intermediaries and interpreters between Nature and Man, rather than boasters and declaimers of other people's work, and these must be admired and esteemed as the object in front of a mirror in comparison to the image seen in the mirror. The first is a real object in and of itself, the second is nothing. These people owe nothing to Nature; it is only good fortune that they wear a human form and, if it weren't for this good fortune, I'd classify them with the cattle and the animals.

There are many who would, with reason, blame me by pointing out that my proofs are contrary to established authority, which is, after all, held in great reverence by their inexperienced minds. They do not realize that my works arise from unadulterated and simple experience, which is the one true mistress, the one true muse. The rules of experience are all that is needed to discern the true from the false; experience is what helps all men to look temperately for the possible, rather than cloaking oneself in ignorance, which can result in no good thing, so that, in the end, one abandons oneself to despair and melancholy.

Among all the studies of natural causes, Light more than anything else delights the beholder, and among the greatest features of Mathematics is the certainty of all its demonstrations which more than anything else elevates the mind of the thinker. Therefore, perspective is to be preferred to all other discourses and systems of knowledge, for in this science the ray of light is explained using methods of demonstration which glorify both Mathematics and Physics and grace the flowers of both these magnificent sciences. But since the axioms of Perspective have been treated extensively, I will abridge them, arranging them in their natural order and the order of their mathematical demonstration. Sometimes I will deduce the effects from their causes, and sometimes I will induce the causes from the effects, while adding my own conclusions that might be inferred from these.