These considerations might enable us, I think, to mark the just frontier of common sense even in this debatable land of psychology.  All that is biological, observable, and documentary in psychology falls within the lines of physical science and offers no difficulty in principle.  Nor need literary psychology form a dangerous salient in the circuit of nature.  The dramatic poet or dramatic historian necessarily retains the presupposition of a material world, since beyond his personal memory (and even within it) he has nothing to stimulate and control his dramatic imagination save knowledge of the material circumstances in which people live, and of the material expression in action or words which they give to their feelings.  His moral insight simply vivifies the scene that nature and the sciences of nature spread out before him:  they tell him what has happened, and his heart tells him what has been felt.  Only literature can describe experience for the excellent reason that the terms of experience are moral and literary from the beginning.  Mind is incorrigibly poetical:  not because it is not attentive to material facts and practical exigencies, but because, being intensely attentive to them, it turns them into pleasures and pains, and into many-coloured ideas.  Yet at every turn there is a possibility and an occasion for transmuting this poetry into science, because ideas and emotions, being caused by material events, refer to these events, and record their order.

All philosophies are frail, in that they are products of the human mind, in which everything is essentially reactive, spontaneous, and volatile:  but as in passion and in language, so in philosophy, there are certain comparatively steady and hereditary principles, forming a sort of orthodox reason, which is or which may become the current grammar of mankind.  Of philosophers who are orthodox in this sense, only the earliest or the most powerful, an Aristotle or a Spinoza, need to be remembered, in that they stamp their language and temper upon human reason itself.  The rest of the orthodox are justly lost in the crowd and relegated to the chorus.  The frailty of heretical philosophers is more conspicuous and interesting:  it makes up the chronique scandaleuse of the mind, or the history of philosophy.  Locke belongs to both camps:  he was restive in his orthodoxy and timid in his heresies; and like so many other initiators of revolutions, he would be dismayed at the result of his work.  In intention Locke occupied an almost normal philosophic position, rendered precarious not by what was traditional in it, like the categories of substance and power, but rather by certain incidental errors—­notably by admitting an experience independent of bodily life, yet compounded and evolving in a mechanical fashion.  But I do not find in him a prickly nest of obsolete notions and contradictions from which, fledged at last, we have flown to our present enlightenment.  In his person, in his temper,