WHAT IS PHILOSOPHY? 519 



sumption: Give me matter and I will huild you a world. . . . But 

 can he make the same boast with reference to the simplest plant or 

 insect? Can he say: Give me matter and I will explain to you the 

 evolution of a caterpillar?" 



Each science endeavors to reduce the most diverse facts with which 

 it deals to identity, to one underlying principle. Heat, light, sound, 

 electricity are different forms of some underlying force or energy. 

 Are states of consciousness referable to the same force, or must we 

 assume another ultimate, of which both physical and mental facts are 

 the expression, as the monists hold? 



All these are problems that are worth considering. The difficulty 

 of solving them and the disagreement existing between the attempts 

 to solve them suggest another problem. The human mind has a tend- 

 ency to unify, to reduce facts to ultimates, to first principles. What 

 Ib the value of this tendency as a means of reaching truth? Can we 

 know anything about these tilings? The instrument of knowledge, 

 the human mind, without which there could be no science at all, is 

 itself a fact which needs to be explained. We evidently employ the 

 same methods in the different branches of knowledge, we explain facts 

 by referring them to their antecedents, simply because this is the func- 

 tion of the mind. But is there no limit to this search for antecedents 

 or causes? What epistemological value has the causal instinct? In 

 fact, what does human knowledge consist in, and how is it possible, as 

 Kant asks? Define its limits, before you set out on the vast sea of 

 speculation. We need a science which will examine the nature and 

 validity of knowledge, a theory of Jcnowledge. As Helmholtz declares, 

 no age can with impunity refuse the task of examining the sources of 

 our knowledge and the ground of its validity. The different sciences 

 employ the categories of thinking without investigating their validity. 

 Philosophy must regard with suspicion everything that is not clear as 

 day ; it is * nothing, if not critical.' In his attempt to explain the 

 sensible world, the scientist often has recourse to the suprasensuous. 

 Can we know anything of the suprasensuous or must we confine our 

 efforts to the study of what our senses present to us ? Must we accept 

 DuBois-Reymond's verdict ? " Concerning the riddles as to what 

 matter and force are, and whether they can think, the natural scienHst 

 must once for all decide upon the verdict: Ignorahimus."* Or shall 

 we protest with Haeckel against the position that there can be invinci- 

 ble barriers to Naturei'Jcennen. There are many other problems which 

 suggest themselves to an epistemology, or theory of knowledge. 



Such a science not only forms the prelude to the most important part 

 of philosophy, to metaphysics, but also assists the thinker in discover- 



* DuBois-Reymond, Orenzen des Naturerkennens. Galileo made a similar 

 statement. 



