 While this argument was once popular (see, e.g., Russell 1923; Hampshire 1952), it soon came to be considered unfit for purpose due to the following considerations. Firstly, it was pointed out that while this way of proceeding may work in certain domains, in the case of other minds the conclusion is logically uncheckable (Locke 1968). Secondly, it was considered problematic that this way of extending one’s knowledge proceeds from a single case (Locke 1968). And thirdly, it was claimed that the very first premise of this argument (I know in my own case) is problematic (Malcolm 1958).