entered. We have seen that this thinking, by virtue of the
consciousness on which it is founded, is impelled always to clothe its
ideas in spatial form. Wherever anything in the pure spatial adjacency
of physical things remains inexplicable, resort is had to hypothetical
pictures whose content consists once more of nothing but spatially
extended and spatially adjacent items. In this way matter came to be
seen as consisting of molecules, molecules of atoms, and atoms of
electrons, protons, neutrons, and so forth.

In so far as scientific thought has held to purely spatial conceptions,
it has been obliged to concentrate on ever smaller and smaller spatial
sizes, so that the spatially conceived atom-picture has finally to
reckon with dimensions wherein the old concept of space loses validity.
When once thinking had started in this direction, it was electricity
which once more gave it the strongest impulse to go even further along
the same lines.

Where we have arrived along this path is brought out in a passage in
Eddington's The Nature of the Physical World. There, after describing
the modern picture of electrons dancing round the atomic nucleus, he
says: 'This spectacle is so fascinating that we have perhaps forgotten
that there was a time when we wanted to be told what an electron is.
This question was never answered. No familiar conceptions can be woven
round the electron; it belongs to the waiting list.' The only thing we
can say about the electron, if we are not to deceive ourselves,
Eddington concludes, is: 'Something unknown is doing we don't know
what.'4

Let us add a further detail from this picture of the atom, as given in
Eddington's Philosophy of Physical Science. Referring to the so-called