For the sake of a uniform terminology we will describe the fact that an instinct cannot be satisfied as ‘frustration’, the means by which this frustration is secured as ‘prohibition’, and the condition produced by the prohibition as ‘privation’. Then the next step is to distinguish between privations that do affect everybody and those that do not, those that merely affect groups, classes, or even individuals. The former are the oldest; with the prohibitions that cause them culture began, who knows how many thousands of years ago, to detach itself from the primordial animal condition of mankind. To our surprise we have found that they are still operative, that they still form the kernel of the hostility to culture. The instinctual wishes that suffer under them are born anew with every child; there is a class of men, the neurotics, who react already to this first group of frustrations by an asocial attitude. Such instinctual wishes are those of incest, of cannibalism, and of murder. It seems strange to classify these, in repudiating which all men seem to be at one, with those others, about whose permissibility or impermissibility in our culture there is so vigorous a dispute; but psychologically one is justified in doing this. Nor is the attitude of culture to these oldest instinctual wishes the same in each case; cannibalism alone seems to be proscribed by everyone, and—to other than analytic observation—completely overcome; the strength of the incest wishes can still be perceived behind the prohibition; and under certain conditions murder is still practised, indeed enjoined, by our culture. It is possible that cultural developments lie before us, in which yet other wish-gratifications, which are to-day entirely permissible, will appear just as disagreeable as those of cannibalism do now.