Yet the chemist and the physicist tell us that these same extended things are not really continuous, as they seem to us to be, but consist of swarms of imperceptible atoms, in rapid motion, at considerable distances from one another in space, and grouped in various ways.
What has now become of the world of realities to which the plain man pinned his faith?
It has come to be looked upon as a world of appearances, of phenomena, of manifestations, under which the real things, themselves imperceptible, make their presence evident to our senses.

Is this new, real world the world of things in which the plain man finds himself, and in which he has felt so much at home?
A closer scrutiny reveals that the world of atoms and molecules into which the man of science resolves the system of material things is not, after all, so very different in kind from the world to which the plain man is accustomed.

He can understand without difficulty the language in which it is described to him, and he can readily see how a man may be led to assume its existence.
The atom is not, it is true, directly perceivable by sense, but it is conceived as though it and its motions were thus perceivable.

The plain man has long known that things consist of parts which remain, under some circumstances, invisible.

When he approaches an object from a distance, he sees parts which he could not see before; and what appears to the naked eye a mere speck without perceptible parts is found under the microscope to be an insect with its full complement of members.