My second speculation is as to the limitations which the structure of language imposes upon the extent of our possible knowledge of the world. I am inclined to think that quite important metaphysical conclusions, of a more or less sceptical kind, can be drawn from simple considerations as to the relation between language and things. A spoken sentence consists of a temporal series of events; a written sentence is a spatial series of bits of matter. Thus it is not surprising that language can represent the course of events in the physical world; it can, in fact, make a map of the physical world, preserving its structure in a more manageable form, and it can do this because it consists of physical events. But if there were such a world as the mystic postulates, it would have a structure different from that of language, and would therefore be incapable of being verbally described. It is fairly clear that nothing verbal can conform or confute this hypothesis. A great deal of the confusion about relations which has prevailed in practically all philosophies comes from the fact that relations are indicated, not by relations, but by words which are as substantial as other words. Consequently, in thinking about relations, we constantly hover between the unsubstantiality of the relation itself and the substantiality of the word. Take, say, the fact that lightning precedes thunder. We saw earlier that to express this by a language closely reproducing the structure of the fact, we should have to say simply: “lightning, thunder”, where the fact that the first word precedes the second means that what the first word means precedes what the second word means. But even if we adopted this method for temporal order, we should still need words for all other relations, because we could not without intolerable ambiguity symbolise them also by the order of our words. When we say “lightning precedes thunder”, the word “precedes” has a quite different relation to what it means from that which the words “lightning” and “thunder” have to what they respectively mean. Wittgenstein[12] says that what really happens is that we establish a relation between the word “lightning” and the word “thunder”, namely the relation of having the word “precedes” between them. In this way he causes relations to be symbolised by relations. But although this may be quite correct, it is sufficiently odd to make it not surprising that people have thought the word “precedes” means a relation in the same sense in which “lightning” means a kind of event. This view, however, must be incorrect. I think it has usually been held unconsciously, and has produced many confusions about relations which cease when it is exposed to the light of day--for example, those which lead Bradley to condemn relations. [12] _Tractatus Logico-Philosophicus_ (Kegan Paul).