ABSTRACT
The view J. S. Mill expounded in his Examination of Sir William Hamilton's Philosophy is best understood as a view of the first kind. According to Mill, the relatively permanent objects of nature are distinct from the sensations we experience, but they are not unknowable things-in-themselves: they are "permanent possibilities of sensation." I see a white piece of paper on the table, Mill said. Although I cease to see the paper when I go into another room, I am persuaded that the paper is still there. My conviction here does not concern an unknowable non-white thing or even a substratum with a Lockean power to produce "ideas" of whiteness; it concerns an objective possibility - the possibility of getting paper-sensations of the sort I had earlier if I return to the room. Mill generalized the point this way:
The conception I form of the world existing at any moment comprises, along with the sensations I am feeling, a countless variety of possibilities of sensation; namely, the whole of those which past observation tells me that I could, under any supposable circumstances, experience at this moment together with an indefinite and illimitable multitude of others which though I do not know that I could, yet it is possible that I might, experience in circumstances not known to me. These various possibilities are the important thing to me in the world. My present sensations are generally of little importance, and are moreover fugitive: the possibilities, on the contrary, are permanent, which is the character that mainly distinguishes our idea of Substance or Matter from our notion of sensation. These possibilities are ... conditional certainties, [ not] ... mere vague possibilities, which experience gives us no warrant for reckoning upon.49 An important feature of these "certified or guaranteed
possibilities of sensation" is that they concern not single sensations but sensations joined together in groups:
When we think of anything as a material substance, or body,
we either have had, or think that on some given supposition we should have, not some one sensation, but a great and even an indefinite number and variety of sensations, generally belonging to different senses, but so linked together that the presence of one announces the possible presence at the very same instant of any or all of the rest.
