It will be seen that among the objects with which we are acquainted are not included physical objects (as opposed to sense-data), nor other people’s minds. These things are known to us by what I call ‘knowledge by description’, which we must now consider.
By a ‘description’ I mean any phrase of the form ‘a so-and-so’ or ‘the so-and-so’. A phrase of the form ‘a so-and-so’ I shall call an ‘ambiguous’ description; a phrase of the form ‘the so-and-so’ (in the singular) I shall call a ‘definite’ description. Thus ‘a man’ is an ambiguous description, and ‘the man with the iron mask’ is a definite description. There are various problems connected with ambiguous descriptions, but I pass them by, since they do not directly concern the matter we are discussing, which is the nature of our knowledge concerning objects in cases where we know that there is an object answering to a definite description, though we are not acquainted with any such object. This is a matter which is concerned exclusively with definite descriptions. I shall therefore, in the sequel, speak simply of ‘descriptions’ when I mean ‘definite descriptions’. Thus a description will mean any phrase of the form ‘the so-and-so’ in the singular.
We shall say that an object is ‘known by description’ when we know that it is ‘the so-and-so’, i.e. when we know that there is one object, and no more, having a certain property; and it will generally be implied that we do not have knowledge of the same object by acquaintance. We know that the man with the iron mask existed, and many propositions are known about him; but we do not know who he was. We know that the candidate who gets the most votes will be elected, and in this case we are very likely also acquainted (in the only sense in which one can be acquainted with some one else) with the man who is, in fact, the candidate who will get most votes; but we do not know which of the candidates he is, i.e. we do not know any proposition of the form ‘A is the candidate who will get most votes’ where A is one of the candidates by name. We shall say that we have ‘merely descriptive knowledge’ of the so-and-so when, although we know that the so-and-so exists, and although we may possibly be acquainted with the object which is, in fact, the so-and-so, yet we do not know any proposition ‘a is the so-and-so’, where a is something with which we are acquainted.
When we say ‘the so-and-so exists’, we mean that there is just one object which is the so-and-so. The proposition ‘a is the so-and-so’ means that a has the property so-and-so, and nothing else has. ‘Mr. A. is the Unionist candidate for this constituency’ means ‘Mr. A. is a Unionist candidate for this constituency, and no one else is’. ‘The Unionist candidate for this constituency exists’ means ‘some one is a Unionist candidate for this constituency, and no one else is’. Thus, when we are acquainted with an object which is the so-and-so, we know that the so-and-so exists; but we may know that the so-and-so exists when we are not acquainted with any object which we know to be the so-and-so, and even when we are not acquainted with any object which, in fact, is the so-and-so.
Common words, even proper names, are usually really descriptions. That is to say, the thought in the mind of a person using a proper name correctly can generally only be expressed explicitly if we replace the proper name by a description. Moreover, the description required to express the thought will vary for different people, or for the same person at different times. The only thing constant (so long as the name is rightly used) is the object to which the name applies. But so long as this remains constant, the particular description involved usually makes no difference to the truth or falsehood of the proposition in which the name appears.
Let us take some illustrations. Suppose some statement made about Bismarck. Assuming that there is such a thing as direct acquaintance with oneself, Bismarck himself might have used his name directly to designate the particular person with whom he was acquainted. In this case, if he made a judgement about himself, he himself might be a constituent of the judgement. Here the proper name has the direct use which it always wishes to have, as simply standing for a certain object, and not for a description of the object. But if a person who knew Bismarck made a judgement about him, the case is different. What this person was acquainted with were certain sense-data which he connected (rightly, we will suppose) with Bismarck’s body. His body, as a physical object, and still more his mind, were only known as the body and the mind connected with these sense-data. That is, they were known by description. It is, of course, very much a matter af chance which characteristics of a man’s appearance will come into a friend’s mind when he thinks of him; thus the description actually in the friend’s mind is accidental. The essential point is that he knows that the various descriptions all apply to the same entity, in spite of not being acquainted with the entity in question.
When we, who did not know Bismarck, make a judgement about him, the description in our minds will probably be some more or less vague mass of historical knowledge—far more, in most cases, than is required to identify him. But, for the sake of illustration, let us assume that we think of him as ‘the first Chancellor of the German Empire’. Here all the words are abstract except ‘German’. The word ‘German’ will, again, have different meanings for different people. To some it will recall travels in Germany, to some the look of Germany on the map, and so on. But if we are to obtain a description which we know to be applicable, we shall be compelled, at some point, to bring in a reference to a particular with which we are acquainted. Such reference is involved in any mention of past, present, and future (as opposed to definite dates), or of here and there, or of what others have told us. Thus it would seem that, in some way or other, a description known to be applicable to a particular must involve some reference to a particular with which we are acquainted, if our knowledge about the thing described is not to be merely what follows logically from the description. For example, ‘the most long-lived of men’ is a description involving only universals, which must apply to some man, but we can make no judgements concerning this man which involve knowledge about him beyond what the description gives. If, however, we say, ‘The first Chancellor of the German Empire was an astute diplomatist’, we can only be assured of the truth of our judgement in virtue of something with which we are acquainted—usually a testimony heard or read. Apart from the information we convey to others, apart from the fact about the actual Bismarck, which gives importance to our judgement, the thought we really have contains the one or more particulars involved, and otherwise consists wholly of concepts.
All names of places—London, England, Europe, the Earth, the Solar System—similarly involve, when used, descriptions which start from some one or more particulars with which we are acquainted. I suspect that even the Universe, as considered by metaphysics, involves such a connexion with particulars. In logic, on the contrary, where we are concerned not merely with what does exist, but with whatever might or could exist or be, no reference to actual particulars is involved.
It would seem that, when we make a statement about something only known by description, we often intend to make our statement, not in the form involving the description, but about the actual thing described. That is to say, when we say anything about Bismarck, we should like, if we could, to make the judgement which Bismarck alone can make, namely, the judgement of which he himself is a constituent. In this we are necessarily defeated, since the actual Bismarck is unknown to us. But we know that there is an object B, called Bismarck, and that B was an astute diplomatist. We can thus describe the proposition we should like to affirm, namely, ‘B was an astute diplomatist’, where B is the object which was Bismarck. If we are describing Bismarck as ‘the first Chancellor of the German Empire’, the proposition we should like to affirm may be described as ‘the proposition asserting, concerning the actual object which was the first Chancellor of the German Empire, that this object was an astute diplomatist’. What enables us to communicate in spite of the varying descriptions we employ is that we know there is a true proposition concerning the actual Bismarck, and that however we may vary the description (so long as the description is correct) the proposition described is still the same. This proposition, which is described and is known to be true, is what interests us; but we are not acquainted with the proposition
