of death in battle, we know, recalls to many, with extreme vividness, scenes of early childhood which they had deemed long since forgotten.  “There is nothing,” says Bergson, “more instructive in this regard than what happens in cases of sudden suffocation—­in men drowned or hanged.  The man, when brought to life again, states that he saw in a very short time all the forgotten events of his life, passing before him with great rapidity, with their smallest circumstances, and in the very order in which they occurred."[Footnote:  La Perception du Changement, pp. 30-31, and Matter and Memory, p 200 (Fr p 168).] Hence we can never be absolutely sure that we have forgotten anything although at any given time we may be unable to recall it to mind.  There is an unconscious memory.[Footnote:  Cf.  Samuel Butler’s Unconscious Memory.] Speaking of the profound and yet undeniable reality of the unconscious, Bergson says,[Footnote:  Matter and Memory, pp 181-182 (Fr. pp. 152-153).  See also Le Souvenir du present et la fausse reconnaissance, Revue philosophique, Dec., 1908, p. 592, and L’Energie spirituelle, pp. 159- 161 (Mind-Energy).] “Our unwillingness to conceive unconscious psychical states, is due, above all, to the fact that we hold consciousness to be the essential property of psychical states, so that a psychical state cannot, it seems, cease to be conscious without ceasing to exist.  But if consciousness is but the characteristic note of the present, that is to say, of the actually lived, in short, of the active, then that which does not act may cease to belong to consciousness without therefore ceasing to exist in some manner.  In other words, in the psychological domain, consciousness may not be the synonym of existence, but only of real action or of immediate efficacy; limiting thus the meaning of the term, we shall have less difficulty in representing to ourselves a psychical state which is unconscious, that is to say, ineffective.  Whatever idea we may frame of consciousness in itself, such as it would be if it could work untrammelled, we cannot deny that in a being which has bodily functions, the chief office of consciousness is to preside over action and to enlighten choice.  Therefore it throws light on the immediate antecedents of the decision and on those past recollections which can usefully combine with it; all else remains in shadow.”  But we have no more right to say that the past effaces itself as soon as perceived than to suppose that material objects cease to exist when we cease to perceive them.  Memory, to use a geometrical illustration which Bergson himself employs, comes into action like the point of a cone pressing against a plane.  The plane denotes the present need, particularly in relation to bodily action, while the cone stands for all our total past.  Much of this past, indeed most of it, only endures as unconscious Memory, but it is always capable of coming to the apex of the cone, i.e., coming into consciousness.  So we may say that there are different planes of Memory, conic sections, if we keep up the original metaphor, and the largest of these contains all our past.  This may be well described as “the plane of dream."[Footnote:  See Matter and Memory, p. 222 (Fr. p. 186) and the paper L’Effort intellectuel, Revue philosophique, Jan., 1902, pp. 2 and 25, L’Energie spirituelle, pp. 165 and 199 (Mind-Energy).]