All knowledge is essentially one. The object-matter upon which intellectexerts itself, does not affect the subjective act of knowing. Physics,when stripped of that which is merely contingent, becomes metaphysics.Physical science deals with object-matter, and discusses the signs bywhich nature communicates her message—that is, phenomena. Metaphysicalscience has to do with the subject-mind, and discusses the meaning ofthe message. The one converts God's hieroglyphics intoeasily-intelligible language; the other translates this language intoIdea. If this be true, there must be a unity of method in all science,however great the diversity of the object-matter investigated. Thismethod is subjectively determined, that is, by the constitution of themind, and not by the particular form of matter upon which intellectualenergy may be exerted. If there is an essential unity in all knowledge,it is because there is a corresponding unity of method in all mentalactivity. It is only when we look upon what is to be known, that truthseparates into sciences; but particular truths become particularsciences only under assumed relations to the whole of which they form a part.
Objectively considered, science is classified knowledge; subjectivelyviewed, it is the laws or principles according to which knowledge isclassified. Every actor implies an act—every[Pg 2] thinker a thought. We maytherefore universally make this dual classification, according as weview the mental operation involved, or the attributes of objects whichform the subject of thought. The possibility of science is conditionedupon the possibility of classification. Mere knowledge is not science,as the world ought to have learned by costly experience. Even classifiedknowledge may not be science; it becomes science not through previousclassification, but in the act of being classified, and therefore onlyas the principle of classification is apprehended—that is, only as theparticular application of the law of generalization is distinctlyrecognized. A man may know a book and know nothing more; he knows thescience only when he is capable of making the book for himself. Mereknowledge thus differs from science in that the one is held only by theapprehensive powers of the mind, while the other passes beyond theseinto the reflective or ratiocinative. Pure science, then, must be whollyabstract. The forms and substances of Nature with which the scientificstudent deals, are only the discrete figures of the young mathematician,to be thrown aside with advancing knowledge. Matter is only the staff onwhich the mind leans, while too feeble to go alone. It is not the finelychiseled statue that renders a man a sculptor; it is the conceptionwhich is therein embodied. A day-laborer may have cut the stone, butonly the artist could conceive the