To the Editors of the Journal of Philosophy, Psychology and Scientific Methods:

In a quotation from the Athenaeum printed in this JOURNAL,¹ I am represented as having said, “there may be perspectives where there are no minds; but we can not know anything of what sort of perspectives they may be, for the sense-datum is mental.” I did not see the Athenaeum, and do not remember what I said, but it can not have been what I am reported as having said, for I hold strongly that the sense-datum is not mental – indeed my whole philosophy of physics rests upon the view that the sense-datum is purely physical. The fact of being a datum is mental, but a particular which is a datum is not logically dependent upon being a datum. A particular which is a datum does, however, appear to be casually dependent upon sense-organs and nerves and brain. Since we carry those about with us, we can not discover what sensibilia, if any, belong to perspectives from places where there is no brain. And since a particular of which we are aware is a sense-datum, we can not be aware of particulars which are not sense-data, and can, therefore, have no empirical evidence as to their nature. This is merely the “egocentric predicament”; it is a tautology, not a “great truth.” It is for this reason, and not because “sense-data are mental,” that we can not know the nature of those perspectives (if any) which belong to places where there are no minds.

I do not know what is the definition of “mental.” In order to obtain a definition, I should first inquire what would necessarily be removed from the world if it were what one would naturally call a world without mind. I see no reason why colors or noises should be removed, but facts which involve such relations as perceiving, remembering, desiring, enjoying, believing would necessarily be removed. This suggests that no particulars of which we have experience are to be called “mental,” but that certain facts, involving certain relations, constitute what is essentially mental in the world of our experience. (I use the word “fact” to designate that which makes a proposition true or false; it includes, I think, everything in the world except what is simple.) The term “mental,” therefore, will be applicable to all facts involving such relations as those enumerated above. This is not yet a definition, since obviously these relations all have some common characteristic, and it must be this characteristic which will yield the proper definition of the term “mental” But I do not know what this characteristic is.

Very truly yours,

B. Russell
Trinity College, Cambridge
June 7, 1915

* “Letter from Bertrand Russell,” The Journal of Philosophy, Psychology and Scientific Methods 12, no. 14 (July 8, 1915), 391-2

¹ Volume 12, page 308