But what kind of reason can be given for believing a proposition of this sort? For believing a proposition which asserts that, since one particular thing exists, it is probable that another particular thing also exists? One thing I think is plain, namely that we can have no good reason for believing such a proposition, unless we have good reason for believing some _generalisation._ It is commonly believed, for instance, that certain so-called flint arrow-heads, which have been discovered, were probably made by prehistoric men; and I think it is plain that we have no reason for believing this unless we have reason to suppose that objects which resemble these in certain particular respects are _generally_ made by men--are _more often_ made by men than by any other agency. Unless certain particular characteristics which those arrow-heads have were characteristics which belonged at least more frequently to articles of human manufacture than to any articles not made by men, it would surely be just as likely as not that these arrowheads were _not_ made by men--that they were, in fact not arrow-heads. That is to say, unless we have reason to assert a _generalisation_--the generalisation that objects of a certain kind are _generally_ made by men, we have no reason to suppose that these particular objects, which are of the kind in question, _were_ made by men. And the same, so far as I can see, is true universally. If we ever have any reason for asserting that, since one particular thing exists, another probably exists or existed or will exist also part of our reason, at least, must consist in reasons for asserting some generalisation--for asserting that the existence of things of a particular kind is, more often than not, accompanied or preceded or followed by the existence of things of another particular kind. It is, I think, sometimes assumed that an alternative to this theory may be found in the theory that the existence of one kind of thing "intrinsically points to," or is "intrinsically a sign or symbol of" the existence of another thing. It is suggested that when a thing which thus points to the existence of another thing exists, then it is at least probable that the thing "pointed to" exists also. But this theory, I think, offers no real alternative. For, in the first place, when we say that the existence of one thing A is a "sign of" or "points to" the existence of another thing B, we very commonly actually mean to say that when a thing like A exists, a thing like B _generally_ exists too. We may, no doubt, mean something else _too_; but this we do mean. We say, for instance, that certain particular words, which we hear or read, are a "sign" that somebody has thought of the particular things which we call the meaning of those words. But we should certainly hesitate to admit that the hearing or reading of certain words could be called a "sign" of the existence of certain thoughts, unless it were true that when those words are heard or read, the thoughts in question _generally_ have existed. If when those words were heard or read, the thoughts had generally _not_ existed, we should say that, in one sense of the word at all events, the hearing of the words was _not_ a sign of the existence of the thoughts. In this sense, therefore, to say that the existence of A "points to" or "is a sign of" the existence of B is actually to say that when A exists, B _generally_ exists also. But, no doubt, the words "points to" "is a sign of" may be used in some other sense: they may, for instance, mean only that the existence of A _suggests_ in some way the belief that B exists. And in such a case we certainly might know that the existence of A pointed to the existence of B, without knowing that when A existed B generally existed also. Let us suppose, then, that in some such sense A does "point to" the existence of B; can this fact give us a reason for supposing it even probable that B existed. Certainly it can, _provided_ it is true that when A _does_ point to the existence of B, B _generally_ exists. But surely it can do so, only on this condition. If when A _points_ to the existence of B, B, nevertheless, does _not_ generally exist, then surely the fact that A points to the existence of B can constitute no probability that B does not exist: on the contrary it will then be probable that, even though A "points to" the existence of B, B does _not_ exist. We have, in fact, only substituted the generalisation that A's _pointing to_ B is generally accompanied by the existence of B, for the generalisation that A's _existence_ is generally accompanied by the existence of B.