the ear of the hearer, then a complicated process in the ear and nerves, and then an event in the brain, which is related to our hearing of the sound in a manner to be investigated later, but is at any rate simultaneous with our hearing of the sound. This gives the physical causal connection between the word spoken and the word heard. There is, however, also another connection of a more psychological sort. When a man utters a word, he also hears it himself, so that the word spoken and the word heard become intimately associated for anyone who knows how to speak. And a man who knows how to speak can also utter any word he hears in his own language, so that the association works equally well both ways. It is because of the intimacy of this association that the plain man identifies the word spoken with the word heard, although in fact the two are separated by a wide gulf.
In order that speech may serve its purpose, it is not necessary, as it is not possible, that heard and spoken words should be identical, but it is necessary that when a man utters different words the heard words should be different, and when he utters the same word on two occasions the heard word should be approximately the same on the two occasions. The first of these depends upon the sensitiveness of the ear and its distance from the speaker; we cannot distinguish between two rather similar words if we are too far off from the man who utters them. The second condition depends upon uniformity in the physical conditions, and is realised in all ordinary circumstances. But if the speaker were surrounded by instruments which were resonant to certain notes but not to certain others, some tones of voice might carry and others might be lost. In that case, if he uttered the same word with two different intonations, the hearer might be quite unable to recognise the sameness. Thus the efficacy of speech depends upon a number of physical conditions. These, however, we will take for granted, in order to come as soon as possible to the more psychological parts of our topic.
Written words differ from spoken words in being material
