Of course those numerous modern philosophers who, like James, try to “find a place for all the experiential facts unencumbered by any hypothesis [like that of an individual substantial soul, presumably] save that of passing states of mind” [_ibid._, p. 480], do not really leave these “states” suspended in mid-air as it were. The imperative need for admitting the reality of substance always ultimately asserts itself: as when James recognizes the necessity of admitting something “more than the bare fact of co-existence of a passing thought with a passing brain-state” [_Principles of Psychology_, i., p. 346—_apud_ MAHER, _ibid._, p. 483]. Only his speculation as to what constitutes this “something ‘more’ which lies behind our mental states” [_ibid._, p. 485] is not particularly convincing: “For my own part,” he says, “I confess that the moment I become metaphysical and try to define the _more_, I find the notion of some sort of an _anima mundi_ thinking in all of us to be a more promising hypothesis, in spite of all its difficulties, than that of a lot of absolutely individual souls” [_ibid._, p. 346—apud MAHER, _ibid._]. This restatement of the medieval pantheistic theory known as Averroïsm, Monopsychism, or the theory of the _intellectus separatus_ [_cf._ DE WULF, _History of Medieval Philosophy_, pp. 381 _sqq._], is a somewhat disappointing contribution to Metaphysics from the most brilliant of our modern psychologists. The “difficulties” of this “more promising hypothesis” had discredited it a rather long time before Professor James resurrected it [_cf._ criticisms—_apud_ MAHER, _ibid._]. CHAPTER X. SOME ACCIDENT-MODES OF BEING: QUALITY. 76. ONTOLOGY AND THE ACCIDENT-MODES OF BEING.—Under the ultimate category or _genus supremum_ of Substance experience reveals to us two broadly distinct sub-classes: corporeal substances, “bodies” or “material” things, and spiritual substances or “spirits”. Of these latter we have direct experience only of one class, _viz._ _embodied_ spirits or human souls. The investigation of the nature of these belongs to _Psychology_, and from the data of that science we may infer, by the light of reason, the _possibility_ of another class of spirits, _viz._ _pure_ spirits, beings of whose actual existence we know from Divine Revelation. The existence of a Supreme Being, Whom we must conceive analogically as substance and spirit, is demonstrated by the light of reason in _Natural Theology_. The investigation of the nature of corporeal substances belongs properly to _Cosmology_. Hence in the present treatise we have no further direct concern with the substance-mode of reality;(322) but only with its accident-modes, and not with all of these.