I spoke a moment ago of the life of which we are “conscious”, and perhaps the reader has been wondering why I have not made more use of the notion of “consciousness”. The reason is that I regard it as only one kind of mnemic effect, and not one entitled to a special place. To say that I am “conscious” of an event is to say that I recollect it, at any rate for a short time after it has happened. To say that I recollect an event is to say that a certain event is occurring in me now which is connected by mnemic causation with the event recollected, and is of the sort that we call a “cognition” of that event. But events which I do not recollect may have mnemic effects upon me. This is the case, not only where we have Freudian suppression, but in all habits which were learnt long ago and have now become automatic, such as writing and speaking. The emphasis upon consciousness has made a mystery of the “unconscious”, which ought to be in no way surprising. It does not much matter which of our two definitions of a “mind” we adopt. Let us, provisionally, adopt the first definition, so that a mind is all the mental events which form part of the history of a certain living body, or perhaps we should rather say a living brain. We can now tackle the question which is to decide whether we are emergent materialists or not, namely: _Is a mind a structure of material units?_ I think it is clear that the answer to this question is in the negative. Even if a mind consists of all the events in a brain, it does not consist of bundles of these events grouped as physics groups them, _i.e._ it does not lump together all the events that make up one piece of matter in the brain, and then all the events that make up another, and so on. Mnemic causation is what concerns us most in studying mind, but this seems to demand a recourse to physics, if we assume, as seems plausible, that mental mnemic causation is due to effects upon the brain. This question, however, is still an open one. If mnemic causation is ultimate, mind is emergent. If not, the question is more difficult. As we saw earlier, there certainly is knowledge in psychology which cannot ever form part of physics. But as this point is important, I shall repeat the argument in different terms.