Errors of Sight

Sight is the first, the noblest, and the most extensive of all the senses; so that if they were given to us to discover the truth, it alone would have a greater share than all the others combined. Thus it will suffice to ruin the authority that the eyes have over reason in order to undeceive us and to lead us to a general distrust of all our senses.

We shall therefore show that we ought not to rely on the testimony of our sight to judge the truth of things in themselves, but only to discover the relation they have to the preservation of our body; that our eyes generally deceive us in everything they represent to us—in the size of bodies, in their figures and movements, in light and in colours, which are the only things we see; that all these things are not as they appear to us; that everyone is deceived by them, and that this casts us into other errors, the number of which is infinite. We begin with extension, and here are the proofs that make us believe that our eyes never show it to us as it truly is.

I. Errors of Sight Regarding Extension Itself

We quite often see through lenses animals much smaller than a grain of sand, which is itself almost invisible; we have even seen animals a thousand times smaller. These living atoms walk as well as other animals. They therefore have legs and feet, bones in those legs to support them (or rather on those legs, for the bones of insects are their skin); they have muscles to move them, tendons, and an infinity of fibres in each muscle, and finally blood or animal spirits, extremely subtle and fine, to fill or to successively move these muscles. Without this, it is impossible to conceive that they live, that they feed themselves, and that they carry their little bodies to different places according to the different impressions of objects; or rather, it is impossible even for those who have spent their whole lives in anatomy and the search for nature to imagine the number, diversity, and delicacy of all the parts of which these little bodies are necessarily composed in order to live and to perform all the things we see them do.

The imagination loses itself and is astonished at the sight of such strange smallness; it cannot reach or grasp parts that offer no hold for it; and although reason convinces us of what has just been said, the senses and imagination oppose it and often oblige us to doubt it.

Our sight is very limited, but it must not limit its object. The idea it gives us of extension has very narrow bounds; but it does not follow from this that extension itself has any. It is undoubtedly infinite in one sense; and this small part of matter, which hides from our eyes, is capable of containing a world in which there would be as many things—though proportionally smaller—as in this great world in which we live. The little animals we have just spoken of perhaps have other little animals that devour them and are imperceptible to them because of their frightful smallness, just as these others are imperceptible to us. What a mite is to us, those animals are to a mite; and perhaps there are in nature smaller ones, and yet smaller ad infinitum, in that strange proportion of a man to a mite.

We have evident and mathematical demonstrations of the infinite divisibility of matter; and that suffices to make us believe that there can be animals smaller and smaller ad infinitum, although our imagination is startled by this thought. God made matter only to form admirable works from it; and since we are certain that there are no parts whose smallness is capable of limiting His power in the formation of these little animals, why should we limit and thus unreasonably diminish the idea we have of an infinite workman, by measuring His power and skill by our imagination, which is finite?

Experience has already partly undeceived us, by showing us animals a thousand times smaller than a mite; why would we want them to be the last and the smallest of all? For my part, I do not see that there is any reason to imagine so. On the contrary, it is much more probable to believe that there are far smaller ones than those that have been discovered; for in the end, small animals are not lacking to microscopes, but microscopes are lacking to small animals.

When, in the middle of winter, one examines the germ of a tulip bulb with a simple magnifying glass or convex lens, or even only with the naked eye, one very easily discovers in this germ the leaves that are to become green, those that are to compose the flower or the tulip, that small triangular part which encloses the seed, and the six little columns that surround it at the base of the tulip. Thus one cannot doubt that the germ of a tulip bulb contains a whole tulip.

It is reasonable to believe the same of the germ of a grain of mustard, of that of an apple pip, and generally of all kinds of trees and plants, although this cannot be seen with the eyes, nor even with the microscope; and one may say with some assurance that all trees exist in miniature within the germ of their seed.

It does not even seem unreasonable to think that there are infinite trees in a single germ, since it contains not only the tree of which it is the seed, but also a very great number of other seeds, which can all contain within themselves new trees and new seeds of trees; which will perhaps still preserve, in an incomprehensible smallness, other trees and other seeds as fecund as the first, and so on to infinity. So that, according to this thought—which can appear impertinent and bizarre only to those who measure the wonders of God’s infinite power by the ideas of their senses and imagination—one might say that in a single apple pip there would be apple trees, apples, and seeds of apple trees for infinite or almost infinite centuries, in that proportion of a perfect apple tree to an apple tree in its seed; that nature merely develops these little trees, by giving a perceptible growth to the one that is outside its seed, and imperceptible but very real growths, proportioned to their size, to those that are conceived to be within their seeds; for one cannot doubt that there can be bodies small enough to insinuate themselves between the fibres of these trees that are conceived within their seeds, and thus to serve as nourishment for them.

What we have just said of plants and their germs can also be thought of animals and the germ from which they are produced. One sees in the germ of a tulip bulb a whole tulip. One also sees in the germ of a fresh egg, which has not been brooded, a chick that is perhaps entirely formed. One sees frogs in the eggs of frogs, and one will see yet other animals in their germ, when one has enough skill and experience to discover them. But the mind must not stop with the eyes; for the sight of the mind has much greater range than the sight of the body. We must therefore think further that all the bodies of men and animals that will be born until the consummation of the ages have perhaps been produced since the creation of the world; I mean that the females of the first animals were perhaps created with all those of the same species that they have engendered, and that were to engender in the course of time.

One could push this thought even further, and perhaps with much reason and truth; but one is rightly afraid of wishing to penetrate too far into the works of God. One sees nothing but infinities there; and not only are our senses and our imagination too limited to comprehend them, but the mind itself, however pure and detached from matter it may be, is too coarse and too weak to penetrate the least of God’s works. It loses itself, it dissipates, it is dazzled, it is frightened at the sight of what is called an atom in the language of the senses. But nevertheless, the pure mind has this advantage over the senses and the imagination: that it recognizes its own weakness and the greatness of God, and that it perceives the infinite in which it loses itself; whereas our imagination and our senses belittle the works of God, and give us a foolish confidence that blindly precipitates us into error. For our eyes do not give us the idea of all those things that we discover with microscopes and by reason. We perceive through our sight no body smaller than a mite or a moth. Half a mite is nothing, if we believe the report it gives us of it. A moth is only a mathematical point in relation to it; one cannot divide it without annihilating it. Our sight therefore does not represent extension to us according to what it is in itself, but only according to what it is in relation to our body; and because half a moth has no considerable relation to our body, and can neither preserve nor destroy it, our sight entirely hides it from us. But if our eyes were made like microscopes, or rather if we were as small as mites and moths, we would judge quite differently of the size of bodies. For without doubt these little animals have eyes disposed to see what surrounds them, and their own bodies as much larger, or as composed of a greater number of parts, than we see them; since otherwise they could not receive from them the impressions necessary for the preservation of their life, and thus the eyes they have would be entirely useless to them.

But in order to be better persuaded of all this, we must consider that our own eyes are in effect only natural lenses; that their humours produce the same effect as the glasses in lenses; and that according to the position they maintain among themselves, and according to the shape of the crystalline lens and its distance from the retina, we see objects differently. So that one cannot assert that there are two men in the world who see them precisely of the same size, or composed of similar parts, since one cannot assert that their eyes are exactly alike.