Being certain that he exists, Descartes next asks ‘what is this “I”?’ ‘What am I?’ ‘I do not yet know,’ he says, ‘clearly enough what I am, I who am certain that I am; so that I must take the greatest care from the start not carelessly to take something else for myself.’ He then rehearses the various things (II Med.: VII 25, HR1 150) that he might be tempted to say that he was. ‘A rational animal’ he rejects as an answer, since it could lead him only into a maze of further doubts, about the meanings of ‘rational’ and ‘animal’; this point brings forward Descartes’s rejection of the traditional scholastic philosophy (to which this phrase, as a deﬁnition of a man, famously belongs) as an instrument for the advance of knowledge. He goes on to consider various other notions, which have in common that they would identify him with some physical thing, either a body or a subtle spirit; these too he rejects, for he has no assurance of the existence of any physical thing. Similarly he rejects various faculties or abilities as belonging to this ‘self’ of his, as again implying the physical; these include even sensation, where this is regarded as implying the physical existence of a body. Following this path, he retreats once more to mere thinking, cogitatio; and here he ﬁnds an attribute that certainly belongs to him: ‘this alone cannot be detached from me’ (VII 27, HR1 150).