Condensing all vital processes in the symbol Vitality, we may say Vitality is requisite for every physiological process. A parallelism may be noted on the subjective side: all the sentient processes may be condensed in the one symbol Sensibility (Feeling), and we must then say, No psychological process is possible as an isolated fact, but demands the co-operation of others--it is a _resultant_ of all the contemporaneous conditions of Sensibility in the organism. In ordinary language this is what is meant by saying that no impression can become a sensation without the intervention of Consciousness--an ambiguous phrase, because of the ambiguity of the term Consciousness, but the phrase expresses the fact that in Sensation a process in the organism is necessary to the reaction of the organ. 32. Having recognized the distinction between the two processes objective and subjective, physical and mental, we have recognized the vanity of attempting to assign their limits, and to say where Motion ends and Feeling begins, or how Feeling again changes into Motion. The one does _not_ begin where the other ends. According to the two-clock theory of Dualism, the two _agents_ move on parallel lines. On the theory of Monism the two _aspects_ are throughout opposed. Both theories explain the facts; which explanation is the most congruous with experience? Against the first we may object that the hypothesis of two Agents utterly unallied in nature wants the cardinal character of a fertile hypothesis in its unverifiableness: it may be true, we can never know that it is true. By the very terms of its definition, the Spirit--if that mean _more_ than an abstract expression of sentient states--is beyond all sensible experience. This is indeed admitted by the dualists, for they postulate a Spirit merely because they cannot otherwise explain the phenomena of Consciousness. Herein they fail to see that even their postulate brings no explanation, it merely restates the old problem in other terms.