Idealism is not possible to infer the 'I' as an object (Descartes' "cogito ergo sum") purely from "the spontaneity of thought". Kant focused on ideas drawn from British philosophers such as Locke, Berkeley and Hume but distinguished his transcendental or critical idealism from previous varieties; Kant distinguished between things as they appear to an observer and things in themselves, "that is, things considered without regard to whether and how they may be given to us". We cannot approach the "noumenon", the "thing in Itself" () without our own mental world. He added that the mind is not a blank slate, "tabula
Cogito, ergo sum in the former case, and an objective thinker in the latter. He argues, first, that it is impossible to make sense of "there is thinking" without relativizing it to "something." However, this something cannot be Cartesian egos, because it is impossible to differentiate objectively between things just on the basis of the pure content of consciousness. The obvious problem is that, through introspection, or our experience of consciousness, we have no way of moving to conclude the existence of any third-personal fact, to conceive of which would require something above and beyond just the purely subjective contents of the mind.