The task which lies before us is to explain how the psychological conception maybe applied to the phenomena of mental disorder, and to show that those phenomena are the result of definite psychological causes operating in accordance with definite psychological laws.

At the outset we encounter an obstacle which, though not perhaps peculiar to the subject we have chosen, offers exceptional difficulties on account of the conditions under which the subject has to be presented. We have to assume that our readers are ignorant, not only of the laws which govern the phenomena of mental disorder, but to a considerable extent of those phenomena themselves. Most readers will have some acquaintance with symptoms occurring in the minor forms of mental disorder known as ‘neuroses’, but few laymen have any practical experience of those occurring in the more pronounced forms of mental disorder included under ‘insanity’. The conception of the insane patient possessed by the public at large is exaggerated and inaccurate. Hence before we can proceed to the explanation of the symptoms which the insane patient exhibits, it is necessary that this erroneous conception should be corrected, and we must ensure that our readers have at any rate a superficial acquaintance with the phenomena which actually occur. It is to this preliminary task that the present chapter is devoted.

To describe in a complete and systematic manner the symptoms met with in the manifold varieties of insanity is obviously impossible within the limits of a small book.