It is true, that certain aestheticians have attempted a distinction between stimuli and stimuli, between _natural and conventional_ signs. They would grant to the former a constant effect on all; to the latter, only on a limited circle. In their belief, signs employed in painting are natural, while the words of poetry are conventional. But the difference between the one and the other is only of degree. It has often been affirmed that painting is a language which all understand, while with poetry it is otherwise. Here, for example, Leonardo placed one of the prerogatives of his art, "which hath not need of interpreters of different languages as have letters," and in it man and brute find satisfaction. He relates the anecdote of that portrait of the father of a family, "which the little grandchildren were wont to caress while they were still in swaddling-clothes, and the dogs and cats of the house in like manner." But other anecdotes, such as those of the savages who took the portrait of a soldier for a boat, or considered the portrait of a man on horseback as furnished with only one leg, are apt to shake one's faith in the understanding of painting by sucklings, dogs, and cats. Fortunately, no arduous researches are necessary to convince oneself that pictures, poetry, and every work of art, produce no effects save on souls prepared to receive them. Natural signs do not exist; because they are all conventional in a like manner, or, to speak with greater exactitude, all are _historically conditioned_. [Sidenote] _The surmounting of variety._ This being so, how are we to succeed in causing the expression to be reproduced by means of the physical object? How obtain the same effect, when the conditions are no longer the same? Would it not, rather, seem necessary to conclude that expressions cannot be reproduced, despite the physical instruments made by man for the purpose, and that what is called reproduction consists in ever new expressions? Such would indeed be the conclusion, if the variety of physical and psychic conditions were intrinsically unsurmountable. But since the insuperability has none of the characteristics of necessity, we must, on the contrary, conclude: that the reproduction always occurs, when we can replace ourselves in the conditions in which the stimulus (physical beauty) was produced. Not only can we replace ourselves in these conditions, as an abstract possibility, but as a matter of fact we do so continually. Individual life, which is communion with ourselves (with our past), and social life, which is communion with our like, would not otherwise be possible. [Sidenote] _Restorations and historical interpretation._