"But in this very raising of an idea to a general idea, to a concept--a process connected with the forming of a sign--is manifested the influence of the lack of hearing and of speech upon the psychical development of the deaf-mute. It appears at first to be an advantage that the sign by which the deaf-mute represents an idea is derived from the impression, the image, the idea, which the user of the sign himself has or has had; he expresses by the sign nothing foreign to him, but only what has become his own. But this advantage disappears when compared with the hindrance caused by this very circumstance in the raising of the individual idea to a general idea, for the fact that the latter is designated by the image, or the elements of the image in which the former consists, is no small obstacle to it in attaining complete generality. The same bond that unites the concept with the conceiver binds it likewise to one of the individual ideas conceived--e. g., when, by pointing to his own flesh, his own skin, he designates the concept flesh, skin (in general also the flesh or the skin of animals); whereas, by means of the word, which the child who has all his senses is obliged to learn, a constraint is indeed exercised as something foreign, but a constraint that simply enforces upon his idea the claim of generality. "One example more. The deaf-mute designates the concept, or general idea, 'red' by lightly touching his lips. With this sign he indicates the red of the sky, of paintings, of dress-stuffs, of flowers, etc. Thus, in however manifold connection with other concepts his concept 'red' may be repeated, it is to him as a concept always _one_ and the same only. It is _common_ to _all_ the connections in which it repeatedly occurs." But before the thinking deaf-mute arrived at the concept "red," he formed for himself the ideas "lip, dress, sky, flower," etc.