‘I think’ is his ultimate premiss. Here the word ‘I’ is really illegitimate; he ought to state his ultimate premiss in the form ‘there are thoughts’. The word ‘I’ is grammatically convenient, but does not describe a datum. When he goes on to say ‘I am a thing which thinks’, he is already using uncritically the apparatus of categories handed down by scholasticism. He nowhere proves that thoughts need a thinker, nor is there reason to believe this except in a grammatical sense.

Bertrand Russell, History of Western Philosop…, loc. 2082