not the sense itself which has been revealed to us in the one case as coloured, and in the other case as hard, but that it is something else which has been thus revealed to us. But it may still be asked, How do we know that we are not deceiving ourselves? How can it be proved that it is the senses, and not something else, which have come before us under the guise of certain sensations? That these sensations are the senses themselves, and nothing but the senses, may be proved in the following manner:—
We bring the matter to the test of actual experiment. We make certain experiments seriatim upon each of the items that lie within the sentient sphere, and we note the effect which each experiment has upon that portion of the contents which is not meddled with. In the exercise of vision, for example, we remove a book, and no change is produced in our perception of a house; a cloud disappears, yet our apprehension of the sea and the mountains, and all other visible things, is the same as ever. We continue our experiments until our test happens to be applied to one particular phenomenon which lies, if not directly, yet virtually, within the sphere of vision. We remove or veil this small visual phenomenon, and a totally different effect is produced from those that took place when any of the other visual phenomena were removed or veiled. The whole landscape is obliterated. We restore this phenomenon, the whole landscape reappears; we adjust this
