§ 3. The attempt to harmonise by reflection the contradictions which beset immediate perception in all its forms is one which is not confined to a single science; the common task of all sciences is to say what, in some special department and for special purposes, must be taken as reality and what as mere appearance, and, by degrading the contradictory to the level of appearance, to satisfy the instinctive demand of our intellect for coherency and consistency of thought. But the development of scientific reflection itself in its turn, while it solves some of our difficulties, is constantly giving rise to fresh perplexities of a higher order. Our scientific principles themselves frequently seem to present us with contradictions of a peculiarly distressing kind. Thus we find ourselves forced in some of our geometrical reasonings to treat a curve as absolutely continuous, in others to regard it as made up of a number of points. Or, again, we are alternately compelled to regard the particles of matter as inert and only capable of being moved by impact from without, and yet again as endowed with indwelling “central forces.” Both the opposing views, in such a case, clearly cannot be ultimately true, and we are therefore compelled either to give up the effort to think consistently, or to face the question, Is either view ultimately true, and if so, which? Again, the principles of one branch of study may appear to contradict those of another. For instance, the absolute determination of every movement by a series of antecedent movements which we assume as a principle in our mechanical science, appears, at least, to conflict with the freedom of human choice and reality of human purpose which are fundamental facts for the moralist and the historian; and we have thus once more to ask, which of the two, mechanical necessity or intelligent freedom, is the reality and which the mere appearance? Finally, the results of our scientific reflection sometimes seem to be in violent disagreement with our deepest and most characteristic aspirations and purposes, and we cannot avoid the question, which of the two have the better title to credit as witnesses to the inmost nature of reality?