When the change is complete, the patient is apt to think of his former self as detached from his present, and of his previous life as a kind of unreal dream; and this fading away of the past into shadowy unreal forms has, as its result, a curious aberration in the sense of time. Thus, it is said that a patient, after being in an asylum only one day, will declare that he has been there a year, five years, and even ten years.[135] This confusion as to self naturally becomes the starting-point of illusions of perception; the transformation of self seeming to require as its logical correlative (for there is a crude logic even in mental disease) a transformation of the environment. When the disease is fully developed under the particular form of monomania, the recollection of the former normal self commonly disappears altogether, or fades away into a dim image of some perfectly separate personality. A new ego is now fully substituted for the old. In other and more violent forms of disease (dementia) the power of connecting the past and present may disappear altogether, and nothing but the _disjecta membra_ of an ego remain. * * * * * Enough has, perhaps, been said to show how much of uncertainty and of self-deception enters into the processes of memory. This much-esteemed faculty, valuable and indispensable though it certainly is, can clearly lay no claim to that absolute infallibility which is sometimes said to belong to it. Our individual recollection, left to itself, is liable to a number of illusions even with regard to fairly recent events, and in the case of remote ones it may be said to err habitually and uniformly in a greater or less degree. To speak plainly, we can never be certain on the ground of our personal recollection alone that a distant event happened exactly in the way and at the time that we suppose. Nor does there seem to be any simple way by mere reflection on the contents of our memory of distinguishing what kinds of recollection are likely to be illusory.