In Aristotle this conception of an end which exhausts all realization and excludes all potentiality appears as a definition of the highest excellence. It of necessity excludes all want and struggle and all dependencies. It is neither practical nor social. Nothing is left but a self-revolving, self-sufficing thought engaged in contemplating its own sufficiency. Some forms of Oriental morals have united this logic with a profounder psychology, and have seen that the final terminus on this road is Nirvana, an obliteration of all thought and desire. In medieval science, the ideal reappeared as a definition of heavenly bliss accessible only to a redeemed immortal soul. Herbert Spencer is far enough away from Aristotle, medieval Christianity and Buddhism; but the idea re-emerges in his conception of a goal of evolution in which adaptation of organism to environment is complete and final. In popular thought, the conception lives in the vague thought of a remote state of attainment in which we shall be beyond "temptation," and in which virtue by its own inertia will persist as a triumphant consummation. Even Kant who begins with a complete scorn for happiness ends with an "ideal" of the eternal and undisturbed union of virtue and joy, though in his case nothing but a symbolic approximation is admitted to be feasible. The fallacy in these versions of the same idea is perhaps the most pervasive of all fallacies in philosophy. So common is it that one questions whether it might not be called _the_ philosophical fallacy. It consists in the supposition that whatever is found true under certain conditions may forthwith be asserted universally or without limits and conditions. Because a thirsty man gets satisfaction in drinking water, bliss consists in being drowned. Because the success of any particular struggle is measured by reaching a point of frictionless action, therefore there is such a thing as an all-inclusive end of effortless smooth activity endlessly maintained. It is forgotten that success is success _of_ a specific effort, and satisfaction the fulfilment _of_ a specific demand, so that success and satisfaction become meaningless when severed from the wants and struggles whose consummations they are, or when taken universally. The philosophy of Nirvana comes the closest to admission of this fact, but even it holds Nirvana to be desirable.