Now the investigation of the economy of nature here contemplated is evidently of the abstract kind. We decompose that economy into its primary phenomena, that is to say, into those which are not reducible to others. These we range in classes, each of which, notwithstanding the connexion that exists between all, requires a separate inductive process; for the existence of laws cannot be proved in any one of them by pure deduction. It is only with these simpler and more abstract relations that our synthesis is directly concerned: when these are established, they afford a rational groundwork for the more composite and concrete researches. The great complexity of concrete relations makes it probable that we shall never be able to co-ordinate them perfectly. In that case the synthesis would always remain limited to abstract laws. But its true object, that of supplying an objective basis for the great synthesis of human life, will none the less be attained. For this groundwork of abstract knowledge would introduce harmony between all our mental conceptions, and thereby would make it impossible to systematize our feelings and actions, which is the object of all sound philosophy. The abstract study of nature is therefore all that is absolutely indispensable for the establishment of unity in human life. It serves as the foundation of all wise action; as the _philosophia prima_, the necessity of which in the normal state of humanity was dimly foreseen by Bacon. When the abstract laws exhibiting the various modes of activity have been brought systematically before us, our practical knowledge of each special system of existence ceases to be purely empirical, though the greater number of concrete laws may still be unknown. We find the best example of this truth in the most difficult and important subject of all, Sociology. Knowledge of the principal statical and dynamical laws of social existence is evidently sufficient for the purpose of systematizing the various aspects of private or public life, and thereby of rendering our condition far more perfect. Should this knowledge be acquired, of which there is now no doubt, we need not regret being unable to give a satisfactory explanation of every state of society that we find existing throughout the world in all ages. The discipline of social feeling will check any foolish indulgence of the spirit of curiosity, and prevent the understanding from wasting its powers in useless speculations; for feeble as these powers are, it is from them that Humanity derives her most efficient means of contending against the defects of the External Order. The discovery of the principal concrete laws would no doubt be attended by the most beneficial results, moral as well as physical; and this is the field in which the science of the future will reap its richest harvest. But such knowledge is not indispensable for our present purpose, which is to form a complete synthesis of