lowered when the electrical waves were harnessed for wireless
telegraphy, or the Roentgen rays were forced into the service of
surgery. The knowledge of nature and the mastery of nature have always
belonged together.

The persistent hesitation of the psychologists to make similar
practical use of their experimental results has therefore come from
different causes. The students of mental life evidently had the
feeling that quiet, undisturbed research was needed for the new
science of psychology in order that a certain maturity might be
reached before a contact with the turmoil of practical life would be
advisable. The sciences themselves cannot escape injury if their
results are forced into the rush of the day before the fundamental
ideas have been cleared up, the methods of investigation really tried,
and an ample supply of facts collected. But this very justified
reluctance becomes a real danger if it grows into an instinctive fear
of coming into contact at all with practical life. To be sure, in any
single case there may be a difference of opinion as to when the right
time has come and when the inner consolidation of a new science is
sufficiently advanced for the technical service, but it ought to be
clear that it is not wise to wait until the scientists have settled
all the theoretical problems involved. True progress in every
scientific field means that the problems become multiplied and that
ever new questions keep coming to the surface. If the psychologists
were to refrain from practical application until the theoretical
results of their laboratories need no supplement, the time for applied
psychology would never come. Whoever looks without prejudice on the
development of modern psychology ought to acknowledge that the
hesitancy which was justified in the beginning would to-day be
inexcusable lack of initiative. For the sciences of the mind too, the