And I wish it to be understood that I am using the words "reason for a belief" in this extremely wide sense. When I look for a good reason for our belief in the existence of other people, I shall not reject any proposition merely on the ground that it only renders their existence probable--only shows it to be more likely than not that they exist. Provided that the proposition in question does render it _positively probable_ that they exist, then, if it also conforms to the conditions which I am about to mention, I shall call it a "good reason." But it is not every proposition which renders it probable that other people exist, which I shall consider to be a good answer to my question. I have just explained that my meaning is wide in one direction--in admitting _some_ propositions which render a belief merely probable; but I have now to explain that it is restricted in two other directions. I do mean to exclude certain propositions which do render that belief probable. When I ask: What reason have _we_ for believing in the existence of other people? a certain ambiguity is introduced by the use of the plural "we." If each of several different persons has a reason for believing that he himself exists, then it is not merely probable, but certain, according to the rules of Formal Logic, that, in a sense, _they_ "have a reason for believing" that several people exist; each has a reason for believing that he himself exists; and, therefore, all of them, taken together, have reasons for supposing that several persons exist. If, therefore, I were asking the question: What reason have _we_ for believing in the existence of other persons? in this sense, it would follow that if each of us has a reason for believing in his own existence, these reasons, taken together, would be a reason for believing in the existence of all of us. But I am not asking the question in this sense: it is plain that this is not its natural sense. What I do mean to ask is: Does _each single one_ of us know any proposition, which is a reason for believing that _others_ exist? I am using "we," that is to say, in the sense of "each of us." But again I do mean _each_ of us: I am not merely asking whether some _one_ man knows a proposition which is a reason for believing that other men exist. It would be possible that some one man, or some few men, should know such a proposition, and yet the rest know no such proposition. But I am not asking whether this is the case. I am asking whether among propositions of the kind which (as we commonly suppose) all or almost all men know, there is any which is a reason for supposing that other men exist. And in asking this question I am not begging the question by supposing that all men do exist. My question might, I think, be put quite accurately as follows. There are certain kinds of belief which, as we commonly suppose, all or almost all men share. I describe this kind of belief as "our" beliefs, simply