"He would find the trail of monsters blindly developing in directions outside all our common imagery of fish and bird; groping and grasping and touching life with every extravagant elongation of horn and tongue and tentacle; growing a forest of fantastic caricatures of the claw and the fin and the finger. But nowhere would he find one finger that had traced one significant line upon the sand; nowhere one claw that had even begun to scratch the faint suggestion of a form. To all appearance, the thing would be as unthinkable in all those countless cosmic variations of forgotten aeons as it would be in the beasts and birds before our eyes The child would no more expect to see it than to see the cat scratch on the wall a vindictive caricature of the dog. The childish common sense would keep the most evolutionary child from expecting to see anything like that; yet in the traces of the rude and recently evolved ancestors of humanity he would have seen exactly that. It must surely strike him as strange that men so remote from him should be so near, and that beasts so near to him should be so remote. To his simplicity it must seem at least odd that he could not find any trace of the beginning of any arts among any animals. That is the simplest lesson to learn in the cavern of the coloured pictures; only it is too simple to be learnt. It is the simple truth that man does differ from the brutes in kind and not in degree; and the proof of it is here; that it sounds like a truism to say that the most primitive man drew a picture of a monkey and that it sounds like a joke to say that the most intelligent monkey drew a picture of a man. Something of division and disproportion has appeared; and it is unique. Art is the signature of man."