reading, arguments of considerable difficulty have to be
taken in their turn.

My principal aim has been to show that these scien-
tific developments provide new material for the philo-
sopher. I have, however, gone beyond this and indicated
how I myself think the material might be used. I realise
that the philosophical views here put forward can only
claim attention in so far as they are the direct outcome
of a study and apprehension of modern scientific work.
General ideas of the nature of things which I may have
formed apart from this particular stimulus from science
are of little moment to anyone but myself. But although
the two sources of ideas were fairly distinct in my mind
when I began to prepare these lectures they have become
inextricably combined in the effort to reach a coherent
outlook and to defend it from probable criticism. For
that reason I would like to recall that the idealistic tinge
in my conception of the physical world arose out of
mathematical researches on the relativity theory. In so
far as I had any earlier philosophical views, they were
of an entirely different complexion.

From the beginning I have been doubtful whether it
was desirable for a scientist to venture so far into
extra-scientific territory. The primary justification for
such an expedition is that it may afford a better view of
his own scientific domain. In the oral lectures it did not
seem a grave indiscretion to speak freely of the various
suggestions I had to offer. But whether they should be
recorded permanently and given a more finished ap-
pearance has been difficult to decide. I have much to
fear from the expert philosophical critic, but I am filled
with even more apprehension at the thought of readers
who may look to see whether the book is "on the side of
the angels" and judge its trustworthiness accordingly.

-viii-