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.