The two sources of ‘pain’ here indicated still do not nearly cover the majority of our painful experiences, but as to the rest one may say with a fair show of reason that their presence does not impugn the supremacy of the pleasure-principle. Most of the ‘pain’ we experience is of a perceptual order, perception either of the urge of unsatisfied instincts or of something in the external world which may be painful in itself or may arouse painful anticipations in the psychic apparatus and is recognised by it as ‘danger’. The reaction to these claims of impulse and these threats of danger, a reaction in which the real activity of the psychic apparatus is manifested, may be guided correctly by the pleasure-principle or by the reality-principle which modifies this. It seems thus unnecessary to recognise a still more far-reaching limitation of the pleasure-principle, and nevertheless it is precisely the investigation of the psychic reaction to external danger that may supply new material and new questions in regard to the problem here treated. II After severe shock of a mechanical nature, railway collision or other accident in which danger to life is involved, a condition may arise which has long been recognised and to which the name ‘traumatic neurosis’ is attached. The terrible war that is just over has been responsible for an immense number of such maladies and at least has put an end to the inclination to explain them on the basis of organic injury to the nervous system due to the operation of mechanical force.[2] The clinical picture of traumatic neurosis approaches that of hysteria in its wealth of similar motor symptoms, but usually surpasses it in its strongly marked signs of subjective suffering—in this resembling rather hypochondria or melancholia—and in the evidences of a far more comprehensive general weakening and shattering of the mental functions. Neither the war neuroses nor the traumatic neuroses of peace are as yet fully understood. With the war neuroses some light was contributed, but also on the other hand a certain confusion introduced, by the fact that the same type of malady could occasionally occur without the interposition of gross mechanical force. In the traumatic neuroses there are two outstanding features which might serve as clues for further reflection: first that the chief causal factor seemed to lie in the element of surprise, in the fright; and secondly that an injury or wound sustained at the same time generally tended to prevent the occurrence of the neurosis. Fright, fear, apprehension are incorrectly used as synonymous expressions: in their relation to danger they admit of quite clear distinction. Apprehension (_Angst_) denotes a certain condition as of expectation of danger and preparation for it, even though it be an unknown one; fear (_Furcht_) requires a definite object of which one is afraid; fright (_Schreck_) is the name of the condition to which one is