Such was the spirit in which, after his long day's work, he added to
his labours in physical science a search in another, and to his notion
a cognate province of thought and speculation. Many a sleepless night
in these years the candle was lighted beside his bed, and for a couple
of hours after midnight he would devour works on philosophy--English,
German, and French, and occasionally Latin. To a mind at once
constructive and intensely critical of unsound construction he added a
quality possessed by few professed philosophers--a large knowledge of
the workings of life, of the human thinking machine, in addition
to various other branches of physical science. As he put it, the
laboratory is the forecourt to the temple of philosophy. For the
method of the laboratory is but the strict application of the one
sound and fruitful mode of reasoning--the method of verification by
experiment. Evidence must be tested before being trusted. The first
duty of such a method is to question in order to find good reason;
Goethe's "tätige Skepsis," a scepticism or questioning which seeks to
overcome itself by finding good standing-ground beyond. Authority as
such is nothing till verified anew. The creeds of ancient sages, the
dogmas of more modern date, must equally bear the light of widening
knowledge and the tests that prove the gold or clay of their
foundations, the stability of the successive steps by which they
proceed.

In all this reading Huxley found nothing to shake what he had learnt
long before from Hamilton--the limits set to human knowledge and
the impossibility of attaining to the ultimate reality behind the
phenomena presented to our cognition. The problems of philosophy, set
forth with unsurpassed clearness for all who will read in our great
English writers, were not solved by soaring into intellectual mists.