KANSAS CITY REVIEW OF SCIENCE. 
that from the time when he made his earliest ciscoveries his mind was not content 
to search after the secrets of nature without, but was equally curious to discover 
the secret of the processes by which man interprets the forces and laws which 
nature hides with such studious reserve. From the time when he began at 
Princeton till the end of his life, this was prominently and avowedly the theme of 
his constant meditation. In making this a study he was not singular among emi- 
nent scientists, but only in that from the beginning to the end this seemed to 
haunt him as the most wonderful problem of all. This habit forced him to con- 
template all the sciences of nature as an organic whole, having intimate relations 
that are broader and deeper than those which are limited to any single class of 
phenomena. It forced him to study and question most closely the process of 
knowledge, the sublimest and most fundamental phenomenon in nature, that he 
might know how far to trust its products, and by what criteria to test its conclu- 
sions. We find evidence of this habit of mind in the questions which he sug- 
gests in his earlier essays, and in the partial solutions which he gives in his mis- 
cellaneous writings. Such a habit would insensibly train him to exalt the human 
intellect in its higher functions, with its principles and laws, its axioms and insti- 
tutions, its theories and anticipations, its forecasting questionings, its creative hy- 
potheses, its tentative theories, and its decisive experiments, and to assure himself 
that an agent or agency such as this could have no affinity with matter and own 
no allegiance with physical laws. Even the suggestion that the thinking agency 
which interprets the universe by authoritative question and answer could once 
have slumbered in a fiery cloud, or could have been evolved from any material 
mind-stufF by any series of physical processes, however daintily phrased, seems 
never to have been entertained by him for an instant as having the semblance of 
scientific probabihty. And yet there is abundant evidence from his writings, both 
early and late, that he was in no sense behind the times, or ignorant of the fasci. 
nating plausibilities of the newest and most fantastic of theories. While he was 
almost the earliest in the field to formulate and defend the doctrine of the cor- 
relation of forces, and to concede that it might be applied to all the processes that 
are properly physiological, he was equally sharp and positive in the assertion tha 
mental agencies of every kind cannot be the correlate of any physical agency 
but are simply directive. He insisted, with equal positiveness, that the so-called 
vital force cannot be the product of any mechanical or chemical activity, single 
or in combination, but must be a directive or constructive agent of itself. Later 
in life he recognized the manifold indications of the presence of a law of progressive 
variation in the history of animal and vegetable life, and so far accepted evolution 
as a working hypothesis. But had he been asked at any time whether evolution 
as a force, or evolution as a law, one or both, apart pr together, could explain the 
origin of life or Uving men with intellect and will, and the capacity for science 
and faith in science, I think he would have regarded the question somewhat as 
though he had been asked whether he believed in the vortices of Descartes, or 
Kepler's directing angels. Had this doctrine been defended in a scientific asso- 
ciation, either in the soaring gyrations of winged speech, or the dry assertions of 
