It is not of course to be inferred that the scientific method will ever abolish the radical distinctions of the Spiritual World. True science proposes to itself no such general leveling in any department. Within the unity of the whole there must always be room for the characteristic differences of the parts, and those tendencies of thought at the present time which ignore such distinctions, in their zeal for simplicity really create confusion. As has been well said by Mr. Hutton: "Any attempt to merge the distinctive characteristic of a higher science in a lower--of chemical changes in mechanical--of physiological in chemical--above all, of mental changes in physiological--is a neglect of the radical assumption of all science, because it is an attempt to deduce representations--or rather misrepresentations--of one kind of phenomena from a conception of another kind which does not contain it, and must have it implicitly and illicitly smuggled in before it can be extracted out of it. Hence, instead of increasing our means of representing the universe to ourselves without the detailed examination of particulars, such a procedure leads to misconstructions of fact on the basis of an imported theory, and generally ends in forcibly perverting the least-known science to the type of the better known."[16] What is wanted is simply a unity of conception, but not such a unity of conception as should be founded on an absolute identity of phenomena. This latter might indeed be a unity, but it would be a very tame one. The perfection of unity is attained where there is infinite variety of phenomena, infinite complexity of relation, but great simplicity of Law. Science will be complete when all known phenomena can be arranged in one vast circle in which a few well known Laws shall form the radii--these radii at once separating and uniting, separating into particular groups, yet uniting all to a common center. To show that the radii for some of the most characteristic phenomena of the Spiritual World are already drawn within that circle by science is the main object of the papers which follow. There will be found an attempt to restate a few of the more elementary facts of the Spiritual Life in terms of Biology. Any argument for Natural Law in the Spiritual World may be best tested in the _a posteriori_ form. And although the succeeding pages are not designed in the first instance to prove a principle, they may yet be entered here as evidence. The practical test is a severe one, but on that account all the more satisfactory. And what will be gained if the point be made out? Not a few things. For one, as partly indicated already, the scientific demand of the age will be satisfied. That demand is that all that concerns life and conduct shall be placed on a scientific basis. The only great attempt to meet that at present is Positivism.