THE idea of collecting these essays occurred to me when, in the leisure
of retire- ment, I scanned some of my own books and found that two of
the more widely read show a startling change of attitude to some of the
fundamental concepts of science. These are Einstein's Theory of
Relativity of 1921 and the American edition of The Restless Universe of
1951. I have taken the introduction of as the former the first item of
this collection, the postscript to the latter as its last. These books
agree in the relativistic concept of space and time, but differ in many
other funda- mental notions. In 1921 I believed-and I shared this belief
with most of my contemporary physicists-that science produced an
objective knowledge of the world, which is governed by deterministic
laws. The scientific method seemed to me superior to other, more
subjective ways of forming a picture of the world- philosophy, poetry,
and religion; and I even thought the unambiguous language of science to
be a step towards a better understanding between human beings. In 1951 I
believed in none of these things. The border between object and subject
had been blurred, deterministic laws had been replaced by statistical
ones, and although physicists understood one another well enough across
all national frontiers they had contributed nothing to a better
understanding of nations, but had helped in inventing and applying the
most horrible weapons of destruction.
