I can see and certainly so far as I shall say, no conclusions can be drawn about any of the subjects about which we most want to know. The only importance I can claim for the subject I shall investigate is that it seems to me to be a matter upon which not Idealists only, but all philosophers and psychologists also, have been in error, and from their erroneous view of which they have inferred (validly or invalidly) their most striking and interesting conclusions. And that it has even this importance I cannot hope to prove. If it has this importance, it will indeed follow that all the most striking results of philosophy—Sensationalism. Agnosticism and Idealism alike—have, for all that has hitherto been urged in their favour, no more foundation than the supposition that a chimera lives in the moon. It will follow that, unless new reasons never urged hitherto can be found, all the most important philosophic doctrines have as little claim to assent as the most superstitious beliefs of the lowest savages. Upon the question what we have reason to believe in the most interesting matters, I do therefore think that my results will have an important bearing; but I cannot too clearly insist that upon the question whether these beliefs are true they will have none whatever.

The trivial proposition which I propose to dispute is this: that esse is percipi. This is a very ambiguous proposition, but, in some sense or other, it has been very widely held. That it is, in some sense, essential to Idealism, I must for the present merely assume. What I propose to show is that, in all the senses ever given to it, it is false.

But, first of all, it may be useful to point out briefly in what relation I conceive it to stand to Idealistic arguments. That wherever you can truly predicate esse you can truly predicate percipi, in some sense or other, is, I take it, a necessary step In all arguments, properly to be called Idealistic, and, what is more, in all arguments hitherto offered for the Idealistic conclusion. If esse is percipi, this is at once equivalent to saying that whatever is, is experienced; and this, again, is equivalent, in a sense, to saying that whatever is, is something mental. But this is not the sense in which the Idealist conclusion must maintain that Reality is mental. The Idealist conclusion is that esse is percipere; and hence, whether esse be percipi or not, a further and different discussion is needed to show whether or not it is also percipere. And again, even if esse be percipere, we need a vast quantity of further argument to show that what has esse has also those higher mental qualities which are denoted by spiritual. This is why I said that the question I should discuss, namely, whether or not esse is percipi, must be utterly insufficient either to prove or to disprove that reality is spiritual. But, on the other hand, I believe that every argument ever used to show that reality is spiritual has inferred this (validly or invalidly) from 'esse is percipere' as one of its premisses; and that this again has never been pretended to be proved except by use of the premiss that esse is percipi. The type of argument used for the latter purpose is familiar enough. It is said that since whatever is, is experienced, and since some things are which are not experienced by the individual, these must at least form part of some experience. Or again that, since an object necessarily implies a subject, and since the whole world must be an object, we must conceive it to belong to some subject or subjects, in the same sense in which whatever is the object of our experience belongs to us. Or again, that, since thought enters into the essence of all reality, we must conceive behind it, in it, or as its essence, a spirit akin to ours, who think: that 'spirit greets spirit' in its object. Into the validity of these inferences I do not propose to enter: they obviously require a great deal of discussion. I only desire to point out that, however correct they may be, yet if esse is not percipi, they leave us as far from a proof that reality is spiritual, as if they were all false too.

But now: Is esse percipi? There are three very ambiguous terms in this proposition, and I must begin by distinguishing the different things that may be meant by some of them.

And first with regard to percipi. This term need not trouble us long at present. It was, perhaps, originally used to mean 'sensation' only; but I am not going to be so unfair to modern Idealists—the only Idealists to whom the term should now be applied without qualification—as to hold that, if they say esse is percipi, they mean by percipi sensation only. On the contrary I quite agree with them that, if esse be percipi at all, percipi must be understood to include not sensation only, but that other type of mental fact, which is called 'thought '; and, whether esse be percipi or not, I consider it to be the main service of the philosophic school, to which modern Idealists belong, that they have insisted on distinguishing 'sensation' and 'thought' and on emphasising the importance of the latter. Against Sensationalism and Empiricism they have maintained the true view. But the distinction between sensation and thought need not detain us here. For, in whatever respects they differ, they have at least this in common, that they are both forms of consciousness or, to use a term that seems to be more in fashion just now, they are both ways of experiencing. Accordingly, whatever esse is percipi may mean, it does at least assert that whatever is, is experienced. And since what I wish to maintain is, that even this is untrue, the question whether it be experienced by way of sensation or thought or both is for my purpose quite irrelevant. If it be not experienced at all, it cannot be either an object of thought or an object of sense. It is only if being involves 'experience' that the question, whether it involves sensation or thought or both, becomes important. I beg, therefore, that percipi may be understood, in what follows, to refer merely to what is common to sensation and thought. A very recent article states the meaning of esse is percipi with all desirable clearness in so far as percipi is concerned.

'I will undertake to show,' says Mr. Taylor,[1] 'that what makes [any piece of fact] real can be nothing but its presence as an inseparable aspect of a sentient experience.' I am glad to think that Mr. Taylor has been in time to supply me with so definite a statement that this is the ultimate premiss of Idealism. My paper will at least refute Mr. Taylor's Idealism, if it refutes anything at all: for I shall undertake to show that what makes a thing real cannot possibly be its presence as an inseparable aspect of a senient experience.

But Mr. Taylor's statement though clear, I think, with regard to the meaning of percipi is highly ambiguous in other respects. I will leave it for the present to consider the next ambiguity in the statement: Esse is percipi. What does the copula mean? What can be meant by saying that Esse is percipi? There are just three meanings, one or other of which such a statement must have, if it is to be true; and of these there is only one which it can have, if it is to be important. (1) The statement may be meant to assert that the word 'esse' is used to signify nothing either more or