Of course the reader to whom the mental physiognomy of ego-maniacs is shown ought always to remember that, if the principal representatives of this species and of that of the mystics are characterized with sufficient clearness, the confines of the latter type are fluctuating. The ego-maniacs are, on the one hand, at once mystics, erotics, and, though it seems paradoxical, even affect occasionally an appearance of philanthropy; among the mystics, on the other hand, we frequently meet with a strongly-developed ego-mania. There are certain specimens among the degenerate in whom all the disorders are produced to such an equal degree that it is doubtful whether they ought to be classed with the mystics or the ego-maniacs. As a general rule, however, co-ordination under one class or the other will not be very difficult. That egoism is a salient feature in the character of the degenerate has been unanimously confirmed by all observers. ‘The degenerate neither knows nor takes interest in anything but himself,’ says Roubinovitch;[233] and Legrain[234] asserts that he ‘has ... only one occupation, that of satisfying his appetites.’ This peculiarity establishes a bond which unites the highest of the degenerate to the lowest, the insane genius to the feeble mental cripple. ‘All delirious geniuses,’ remarks Lombroso, ‘are very much captivated by, and preoccupied with, their own selves,’[235] and Sollier writes on the subject of their antipodes, the imbeciles: ‘Undisciplined as they are, they obey only through fear, are often violent, especially to those who are weaker than themselves, humble and submissive towards those they feel to be stronger. They are without affection, egoistic in the highest degree, braggarts.’[236] The clinicist is satisfied with indicating the fact of this characteristic egoism, but for ourselves we wish further to investigate what are its organic roots, why the degenerate must be more than egoistic, why he must be an ego-maniac, and cannot be otherwise. In order to understand how the consciousness of the ‘I’ (morbidly exaggerated and frequently increasing to megalomania) originates, we must recall how the healthy consciousness of the ‘I’ is formed. It is, of course, not my intention here to treat of the whole theory of cognition. It is only the most important results of this science, so highly developed in the present day, that can find place in this work. It has become a philosophical commonplace that we know directly only those changes which take place in our own organism. If, in spite of this, we are able to form an image of the external world surrounding us, from perceptions derived only from within, it is because we trace the changes in our organism which we have perceived to causes exterior to it; and from the nature and force of the changes taking place in our organism draw conclusions as to the nature and force of the external events causing them.