[146] For a description of each of these extremes of boundless gaiety and utter despondency, see Griesinger, _op. cit._, Bk. III. ch. i. and ii. The relation of pessimism to pathological conditions is familiar enough; less familiar is the relation of unrestrained optimism. Yet Griesinger writes that among the insane "boundless hilarity," with "a feeling of good fortune," and a general contentment with everything, is as frequent as depression and repining (see especially p. 281, also pp. 64, 65). [147] It has been seen that, from a purely psychological point of view, even what looks at first like pure presentative cognition, as, for example, the recognition of a present feeling of the mind, involves an ingredient of representation. [148] See especially what was said about the _rationale_ of illusions of perception, pp. 37, 38. [149] I say "usually," because, as we have seen, there may sometimes be a permanent and even an inherited predisposition to active illusion in the individual temperament and nervous organization. [150] See what was said on the nature of passive illusions of sense (pp. 44, 68, 70, etc.) The logical character of illusion might be brought out by saying that it resembles the fallacy which is due to reasoning from an approximate generalization as though it were a universal truth. In thus identifying illusion and fallacy, I must not be understood to say that there is, strictly speaking, any such thing as an unconscious reasoning process. On the contrary, I hold that it is a contradiction to talk of any _mental_ operation as altogether unconscious. I simply wish to show that, by a kind of fiction, illusion may be described as the result of a series of steps which, if separately unfolded to consciousness (as they no longer are), would correspond to those of a process of inference. The fact that illusion arises by a process of contraction out of conscious inference seems to justify this use of language, even apart from the fact that the nervous processes in the two cases are pretty certainly the same. [151] If we turn from the region of physical to that of moral ideas, we see this historical collision between common and individual conviction in a yet more impressive form. The teacher of a new moral truth has again and again been set down to be an illusionist by a society which was itself under the sway of a long-reigning error. As George Eliot observes, "What we call illusions are often, in truth, a wider vision of past and present realities--a willing movement of a man's soul with the larger sweep of the world's forces." [152] To make this account of the philosophic problem of the object-world complete, I ought to touch not only on the distinction between the vulgar and the scientific view of material things, but also on the distinction, within physical science, between the less and the more abstract view roughly represented by molar and molecular physics.