By the middle of the nineteenth century the empirical sciences had undergone vast expansion in the study of detail and in the discovery of principles. Men felt the necessity of some adequate discussion of the relation of these sciences one to another and of their unity. There was need of the organisation of the mass of knowledge, largely new and ever increasing, which the sciences furnished. It lay in the logic of the case that some of these attempts should advance the bold claim to deal with all knowledge whatsoever and to offer a theory of the universe as a whole. Religion, both in its mythological and in its theological stages, had offered a theory of the universe as a whole. The great metaphysical systems had offered theories of the universe as a whole. Both had professed to include all facts. Notoriously both theology and metaphysics had dealt in most inadequate fashion with the material world, in the study of which the sciences were now achieving great results. Indeed, the methods current and authoritative with theologians and metaphysicians had actually prevented study of the physical universe. Both of these had invaded areas of fact to which their methods had no application and uttered dicta which had no relation to truth. The very life of the sciences depended upon deliverance from this bondage. The record of that deliverance is one of the most dramatic chapters in the history of thought. Could one be surprised if, in the resentment which long oppression had engendered and in the joy which overwhelming victory had brought, scientific men now invaded the fields of their opponents? They repaid their enemies in their own coin. There was with some a disposition to deny that there exists an area of knowledge to which the methods of metaphysicians and theologians might apply. This was Comte's contention. Others conceded that there might be such an area, but claimed that we can have no knowledge of it. Even the theologians, after their first shock, were disposed to concede that, concerning the magnitudes in which they were most interested, as for example, God and soul, we have no knowledge of the sort which the method of the physical sciences would give. They fell back upon Kant's distinction of the two reasons and two worlds. They exaggerated the sharpness of that distinction. They learned that the claim of agnosticism was capable of being viewed as a line of defence, behind which the transcendental magnitudes might be secure. Indeed, if one may take Spencer as an example, it is not certain that this was not the intent of some of the scientists in their strong assertion of agnosticism. Spencer's later work reveals that he had no disposition to deny that there are foundations for belief in a world lying behind the phenomenal, and from which the latter gets its meaning.