r. It does not occur to me to maintain that the house changes
as I advance. But, at a given instant, changes of a different sort
make their appearance. Smoke arises, and flames burst from the roof.
Now I have no hesitation in saying that changes are taking place in the
house. It would seem foolish to describe the occurrence as a mere
change in my sensations. Before it was my sensations that changed; now
it is the house itself.

We are drawing this distinction between changes in our sensations and
changes in things at every hour in the day. I cannot move without
making things appear and disappear. If I wag my head, the furniture
seems to dance, and I regard it as a mere seeming. I count on the
clock's going when I no longer look upon its face. It would be absurd
to hold that the distinction is a mere blunder, and has no foundation
in our experience. The role it plays is too important for that. If we
obliterate it, the real world of material things which seems to be
revealed in our experience melts into a chaos of fantastic experiences
whose appearances and disappearances seem to be subject to no law.

And it is worthy of remark that it is not merely in common life that
the distinction is drawn. Every man of science must give heed to it.
The psychologist does, it is true, pay much attention to sensations;
but even he distinguishes between the sensations which he is studying
and the material things to which he relates them, such as brains and
sense-organs. And those who cultivate the physical sciences strive,
when they give an account of things and their behavior, to lay before
us a history of changes analogous to the burning of the stick and of
the house, excluding mere changes in sensations.

There is no physicist or botanist or zooelogist who has not our common
experience that things as perceived by us--our experiences of
things--appear or disappear or change their character when we open or
shut our eyes or move about. But nothing of all this appears in their
books. What they are concerned with is things and their changes, and
they do not consider such matters as these as falling within their
province. If a botanist could not distinguish between the changes
which take place in a plant, and the changes which take place in his
sensations as he is occupied in studying the plant, but should tell us
that the plant grows smaller as one recedes from it, we should set him
down as weak-minded.

That the disti