Idealists admit that some things really exist of which they are not aware: there are some things, they hold, which are not inseparable aspects of _their_ experience, even if they be inseparable aspects of some experience. They further hold that some of the things of which they are sometimes aware do really exist, even when they are not aware of them: they hold for instance that they are sometimes aware of other minds, which continue to exist even when they are not aware of them. They are, therefore, sometimes aware of something which is _not_ an inseparable aspect of their own experience. They do _know some_ things which are _not_ a mere part or content of their experience. And what my analysis of sensation has been designed to show is, that whenever I have a mere sensation or idea, the fact is that I am then aware of something which is equally and in the same sense _not_ an inseparable aspect of my experience. The awareness which I have maintained to be included in sensation is the very same unique fact which constitutes every kind of knowledge: "blue" is as much an object, and as little a mere content, of my experience, when I experience it, as the most exalted and independent real thing of which I am ever aware. There is, therefore, no question of how we are to "get outside the circle of our own ideas and sensations." Merely to have a sensation is already to _be_ outside that circle. It is to know something which is as truly and really _not_ a part of _my_ experience, as anything which I can ever know. Now I think I am not mistaken in asserting that the reason why Idealists suppose that everything which _is_ must be an inseparable aspect of some experience, is that they suppose some things, at least, to be inseparable aspects of _their_ experience. And there is certainly nothing which they are so firmly convinced to be an inseparable aspect of their experience as what they call the _content_ of their ideas and sensations. If, therefore, _this_ turns out in every case, whether it be also the content or not, to be at least _not_ an inseparable aspect of the experience of it, it will be readily admitted that nothing else which _we_ experience ever is such an inseparable aspect. But if we never experience anything but what is _not_ an inseparable aspect of _that_ experience, how can we infer that anything whatever, let alone _everything,_ is an inseparable aspect of _any_ experience? How utterly unfounded is the assumption that "_esse_ is _percipi"_ appears in the clearest light.