 In The Blue and Brown Books, Wittgenstein distinguishes between two uses of the term “I” which he calls the “use as subject” and the “use as object” (1958: 66–70; Garrett 1998: ch. 8; cf. James’ distinction between the I, or pure ego, and the me, or empirical self (1890: vol. 1, ch. X)). As Wittgenstein describes the difference, there is a certain kind of error in thought that is possible when “I” is used as object but not when “I” is used as subject. Wittgenstein notes that if I find myself in a tangle of bodies, I may wrongly take another’s visibly broken arm to be my own, mistakenly judging “I have a broken arm”. Upon seeing a broken arm, then, it can make sense to wonder whether or not it is mine. If, however, I feel a pain in the arm, and on that basis judge “I have a pain”, then it makes no sense at all for me to wonder whether the pain of which I am aware is mine. That is, it is not possible for me to be aware, in the ordinary way, of a pain in an arm but mistakenly judge it to be my own arm that hurts. On this picture, self-ascriptions of pain, at least when based on the usual introspective grounds, involve the use of “I” as subject and so are immune to this sort of error of misidentification.