It means, first, that new experiences have supervened; and, second, that they have borne a certain assignable relation to the unit supposed. Continue, if you please, to speak of the pure unit as 'the pen.' So far as the pen's successors do but repeat the pen or, being different from it, are 'energetically'[70] related to it, it and they will form a group of stably existing physical things. So far, however, as its successors differ from it in another well-determined way, the pen will figure in their context, not as a physical, but as a mental fact. It will become a passing 'percept,' _my_ percept of that pen. What now is that decisive well-determined way? In the chapter on 'The Self,' in my _Principles of Psychology_, I explained the continuous identity of each personal consciousness as a name for the practical fact that new experiences[71] come which look back on the old ones, find them 'warm,' and greet and appropriate them as 'mine.' These operations mean, when analyzed empirically, several tolerably definite things, viz.: 1. That the new experience has past time for its 'content,' and in that time a pen that 'was'; 2. That 'warmth' was also about the pen, in the sense of a group of feelings ('interest' aroused, 'attention' turned, 'eyes' employed, etc.) that were closely connected with it and that now recur and evermore recur with unbroken vividness, though from the pen of now, which may be only an image, all such vividness may have gone; 3. That these feelings are the nucleus of 'me'; 4. That whatever once was associated with them was, at least for that one moment, 'mine'--my implement if associated with hand-feelings, my 'percept' only, if only eye-feelings and attention-feelings were involved. The pen, realized in this retrospective way as my percept, thus figures as a fact of 'conscious' life. But it does so only so far as 'appropriation' has occurred; and appropriation is _part of the content of a later experience_ wholly additional to the originally 'pure' pen. _That_ pen, virtually both objective and subjective, is at its own moment actually and intrinsically neither. It has to be looked back upon and _used_, in order to be classed in either distinctive way. But its use, so called, is in the hands of the other experience, while _it_ stands, throughout the operation, passive and unchanged. If this pass muster as an intelligible account of how an experience originally pure can enter into one consciousness, the next question is as to how it might conceivably enter into two. III