To the same effect Mr. Tylor says, in the passage already quoted, that deaf-mutes cannot form ideas of any save the lowest degree of abstraction, and further on he gives some interesting illustrations of the fact. Thus, for instance, a deaf-mute who had been educated said that before his instruction his fingers had taught him his numbers, and that when the number was over ten, he made notches on a piece of wood. Here we see the inherited capability of numerical computation united with the crudest form of numerical notation, or symbolism. And so in all other cases of deaf-mutes before instruction; they present an inherited capacity of abstract ideation, and yet do not find their sign-language of much service in assisting them to develop this capacity: it is too essentially pictorial to go far beyond the region of sensuous perception. Thus, on the whole, although I deem it profitless to speculate on what the language of gestures might have become in the absence of speech, I think it is highly questionable whether it would have reached any considerable level of excellence; and I think it is not improbable that, in the absence of articulation, the human race would not have made much psychological advance upon the anthropoid apes. For we must never forget the important fact that thought is quite as much the effect as it is the cause of language, whether of speech or of gesture; and seeing how inferior gesture is to speech as a system of language, especially in regard to precision and abstraction, I do not think it probable that, in the absence of speech, gesture alone would have supplied the exact and delicate conditions which are essential to the growth of any highly elaborate ideation.