We have seen that Kant made free use of the metaphor of giving and receiving. But it is hardly possible to use such metaphors and retain independence of judgment. The associations customarily attached to the figurative language carry one away easily, and often for a long way, on the familiar paths of imagination. The analogy is used even where--if all were looked into--its terms become meaningless. No reader of Locke can have failed, e. g., to notice how he is misled by his own images of the dark room and the empty cabinet:--images, useful and perhaps even necessary, but requiring constant restraint in him who would ply them wisely and to his reader's good. From what has been said above it will be clear that the acquisition of experience, the growth of knowledge, is a unique species of gift and acceptance. The consciousness which Kant describes may be the consciousness of John Doe or Richard Roe: but as Kant describes it, the limitations of their personality, i.e. of their individual body and soul, have been neglected. It is consciousness in general which is Kant's theme, just as it is granite in general--and not the block in yonder field,--which is the theme of the geologist. Once get that clear, and you will also see clearly that consciousness is at once giver and recipient--neither or both: at once receptivity and spontaneity. But--you may reply--does not the material object _act_ (chemically, optically, mechanically, &c.) on the sense-organ on the periphery of my body, does not the nerve-string _convey_ the impression to the brain; and is not perception the _effect_ of that process, in which the material object is the initial _cause_?
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.