At any moment we are in possession of certain information, that is, of cognitions which have been logically derived by induction and hypothesis from previous cognitions which are less general, less distinct, and of which we have a less lively consciousness. These in their turn have been derived from others still less general, less distinct, and less vivid; and so on back to the idealn first, which is quite singular, and quite out of consciousness. This ideal first is the particular thing-in-itself. It does not exist as such. That is, there is no thing which is in-itself in the sense of not being relative to the mind, though things which are relative to the mind doubtless are, apart from that relation.
nBy an ideal, I mean the limit which the possible cannot attain.
A real is anything that is not affected by men’s cognitions about it. An external object is anything that is not affected by any of man’s cognitions (whether about it or about anything else) to whom it is external. Exaggerate this, and you have the conception of what is not affected by any human cognitions. Take the converse of this definition, and you have the definition of the Ding an sich, as that which does not affect human cognition.