.
We commonly have had to deal with probabilities which arise through ignorance. With fuller knowledge we should sweep away the references to probability and substitute the exact facts. But it appears to be a fundamental point in Schrödinger’s theory that his probabilities are not to be replaced in that way. When his
is sufficiently concentrated it indicates the point where the electron is; when it is diffused it gives only a vague indication of the position. But this vague indication is not something which ideally ought to be replaced by exact knowledge; it is
itself which acts as the source of the light emitted from the atom, the period of the light being that of the beats of
. I think this means that the spread of