What is a Naturalist? I venture upon the following definition:—A man with a native gift for science who has taken to art. His purpose is not to extract the material and spiritual significance of objects, thus communicating them to us more rapidly and intensely than we should perceive them ourselves, and thereby giving us a sense of heightened vitality; his purpose is research, and his communication consists of nothing but facts. From this perhaps too abstract statement let us take refuge in an example already touched upon—the figure of the Almighty in Uccello’s “Sacrifice of Noah.” Instead of presenting this figure as coming toward us in an attitude and with an expression that will appeal to our sense of solemnity, as a man whose chief interest was artistic would have done—as Giotto, in fact, did in his “Baptism”—Uccello seems to have been possessed with nothing but the scientific intention to find out how a man swooping down head-foremost would have looked if at a given instant of his fall he had been suddenly congealed and suspended in space. A figure like this may have a mathematical but certainly has no psychological significance. Uccello, it is true, has studied every detail of this phenomenon and noted down his observations, but because his notes happen to be in form and colour, they do not therefore constitute a work of art. Wherein does his achievement differ in quality from a coloured map of a country? We can easily conceive of a relief map of Cadore or Giverny on so large a scale, and so elaborately coloured, that it will be an exact reproduction of the physical aspects of those regions, but never for a moment should we place it beside a landscape by Titian or Monet, and think of it as a work of art. Yet its relation to the Titian or Monet painting is exactly that of Uccello’s achievement to Giotto’s. What the scientist who paints—the naturalist, that is to say,—attempts to do is not to give us what art alone can give us, the life-enhancing qualities of objects, but a reproduction of them as they are. If he succeeded, he would give us the exact visual impression of the objects themselves, but art, as we have already agreed, must give us not the mere reproductions of things but a quickened sense of capacity for realising them. Artistically, then, the naturalists, Uccello and his numerous successors, accomplished nothing. Yet their efforts to reproduce objects as they are, their studies in anatomy and perspective, made it inevitable that when another great genius did arise, he should be a Leonardo or a Michelangelo, and not a Giotto.