In this exposition--which is not unknown in vulgar philosophy--there is a monstrous, almost inextricable, complication of fact with inference, of truth with error. So long as there is an uncertainty--and metaphysicians themselves, we may be reminded, are not agreed upon the matter--as to what we are to understand by cause, effect, and act, what an impression is, and how brain and intelligence mutually stand to each other, it is hardly possible to pronounce judgment upon this mode of statement. Yet perhaps we may go so far as to say that while the terms quoted bear an intelligible meaning when applied within the physiological process they are vain when used of relations of mind to body. There is a sense in which we may speak of the action of mind on body, and of body on mind: but what we mean would perhaps be more unmistakably expressed by saying that the higher intellectual and volitional energies are never in our experience entirely independent of the influences of the lower sensitive and emotional nature. In the metaphysical sense which the terms are here made to bear, they mislead. Action and re-action can only take place in the separateness of space, where one is here and another there: (though, be it added, they cannot take place even on these terms, unless the here and the there be somehow unified in a medium which embraces both). _Mens_, said Spinoza, is the _idea corporis_[1]: he would hardly have said _Corpus habet ideam_. What he meant would scarcely have been well described by calling it a _parallelism_ or mutual independence, yet with harmony or identity, of body and mind. Apart from body, no doubt, mind is for him a nullity: for body is what gives it reality. But, on the other hand, Mind is the enveloping and including 'Attribute' of the two: idealism overlaps realism. This was the fundamental proposition which Kant contended for; what he spoke of as his own Copernican discovery: though, in reality, for the _student_ of the history of philosophy it was only the re-statement, in some respects the clearer statement, of the idealism which even Hume, not to mention Spinoza and Leibniz, had maintained. The world of experience--the empirical, objective, and real world--is a world of ideas, of representations which have place only in mind, of appearances. Space and time are subjective: the forms of thought are subjective: and yet they constitute phenomenal or empirical or real objectivity. Such language is--it would seem inevitably--misunderstood: and in his second edition, Kant--besides many other minor modifications of statement,--had to defend himself by inserting a 'confutation of idealism,' i.e. of the theory which holds that the existence of objects outside us in space is doubtful, if not even impossible. But no end of argument will ever confute the view that Kant's doctrine is such idealism: until people can be got to rise to a new view of what is subjectivity--what is an idea--and what is existence outside us.