INTRODUCTION 7 



It is obvious that if this mode of philosophising (which recalls 

 the mystical phenomenalism of Berkeley with his " esse est 

 percipi") is to give us a monistic representation free from all 

 hypothesis, not only the chemical concept of atoms, but also the 

 physical concept of energy must be given up, the psychical concept 

 of sensations alone being retained as the ultimate homogeneous 

 and irreducible element of reality. To be strictly logical, we 

 must cancel the entire doctrine of physics and chemistry, as based 

 upon mere hypothesis, and throw ourselves into the arms of pure 

 psychology, which alone enjoys the privilege of having for its 

 content the aggregates of the homogeneous elements of reality ! 

 But how can we understand the manifold qualitative differences in 

 these aggregates, if once we admit them to arise from qualitatively 

 identical elements ? How conceive of physical facts, and what in 

 common parlance is called the " external world," as a complex of 

 sensations, if we make an abstraction of the internal world, by 

 means of which alone these are to arise as such in consciousness ? 

 How can the physiologist imagine a sensation as divorced from 

 the law of causality and independent of the stimulus that excites 

 it ? Is it not absurd to admit an essential identity between the 

 esse and the nosse, the esse and the posse ? How are we to 

 reconcile Mach's view, according to which the psychical fact is 

 presented as something less real than almost (as it were) a 

 shadow of the physical fact, with his general doctrine, according 

 to which the physical and the psychical are said to be identical 

 in their nature ? 



If we inquire from the followers of Mach what pragmatic 

 value can attach to Psychical Monism (or Phenomenalism, or 

 Empirical Criticism, as it is termed by others) they admit that 

 it is nil when we are concerned with scientific work in the 

 various fields of research. " Here all remains as before " (writes 

 Max Verworn, 1905), " methods, symbols, facts, relations are all 

 untouched. Scientific work pursues its course unchecked." This 

 is equivalent to an admission that both the atomistic and the 

 energetic hypotheses (which constitute Materialism), and the 

 hypothesis of vital or psychical force (which constitutes Neo- 

 vitalism), must continue to function as indispensable instruments, 

 as poles or presumptions necessary to future discoveries and to 

 the progress of science in general. In order to build up science 

 we are constrained to descend from the rarefied regions of abstrac- 

 tion, and to live in the world of concrete facts, grappling with 

 the vital processes in their varied and complex phenomenology, 

 whether mechanical or psychical ; in other words, Monism must 

 be completed by Pluralism, according to our immediate experi- 

 ence. 



Each new physiological experiment, each new scientific 

 conquest, appears as a more or less important integration of the 



