One cannot but be struck with the fact that in many (if not in most) attacks of acute insanity the patient, on recovery, has no recollection of the incidents of the illness. She may have answered our questions in a way showing that at the time there was not only a consciousness of a certain kind present, but also the capacity for understanding and replying in accordance with her ideas (however unfounded they may, in fact, be), and yet on recovery, or even in a temporary lucid interval, all remembrance of the disordered state has passed away, and that, too, beyond the capacity of recall—nothing but a misty, hazy remembrance of some condition which has been passed through remains, just as one finds it impossible to re-instate the details of a dream, the reality of which was at the time vivid in consciousness. We have here to deal with a dual consciousness, a knowledge of states apparently incompatible with, and distinct from, each other. We are all familiar with states of acute mental disturbance where there is difficulty in making the patient understand what we are saying—not necessarily difficult or involved questions, but simple queries relating to what we think are matters in the patient‘s consciousness, such as it is. Here it is doubtful if the patients really understand what we are saying, though there is no doubt about their hearing the question, e.g., they may hear the question but the reply will be merely the reiteration of some particular delusion which has no connection with the question, or there need not be any reply at all, as if we were addressing them in a foreign language which they did not understand, or as if what is said to them has a different meaning from what is intended.