When a ghostly sphere, containing memory and all ideas, has been distinguished from the material world, it tends to grow at the expense of the latter, until nature is finally reduced to a mathematical skeleton. This skeleton itself, but for the need of a bridge to connect calculably episode with episode in experience, might be transferred to mind and identified with the scientific thought in which it is represented. But a scientific theory inhabiting a few scattered moments of life cannot connect those episodes among which it is itself the last and the least substantial; nor would such a notion have occurred even to the most reckless sceptic, had the world not possessed another sort of reputed reality—the minds of others—which could serve, even after the supposed extinction of the physical world, to constitute an independent order and to absorb the potentialities of being when immediate consciousness nodded. But other men’s minds, being themselves precarious and ineffectual, would never have seemed a possible substitute for nature, to be in her stead the background and intelligible object of experience. Something constant, omnipresent, infinitely fertile is needed to support and connect the given chaos. Just these properties, however, are actually attributed to one of the minds supposed to confront the thinker, namely, the mind of God. The divine mind has therefore always constituted in philosophy either the alternative to nature or her other name: it is _par excellence_ the seat of all potentiality and, as Spinoza said, the refuge of all ignorance. Speculative problems would be greatly clarified, and what is genuine in them would be more easily distinguished from what is artificial, if we could gather together again the original sources for the belief in separate minds and compare these sources with those we have already assigned to the conception of nature. But speculative problems are not alone concerned, for in all social life we envisage fellow-creatures conceived to share the same thoughts and passions and to be similarly affected by events. What is the basis of this conviction? What are the forms it takes, and in what sense is it a part or an expression of reason? This question is difficult, and in broaching it we cannot expect much aid from what philosophers have hitherto said on the subject. For the most part, indeed, they have said nothing, as by nature’s kindly disposition most questions which it is beyond a man’s power to answer do not occur to him at all. The suggestions which have actually been made in the matter may be reduced to two: first, that we conceive other men’s minds by projecting into their bodies those feelings which we immediately perceive to accompany similar operations in ourselves, that is, we infer alien minds by analogy; and second, that we are immediately aware of them and feel them to be friendly or hostile counterparts of our own thinking and effort, that is, we evoke them by dramatic imagination.