III

MEANS AND ENDS


Applied psychology is evidently to be classed with the technical
sciences. It may be considered as psychotechnics, since we must
recognize any science as technical if it teaches us to apply
theoretical knowledge for the furtherance of human purposes. Like all
technical sciences, applied psychology tells us what we ought to do if
we want to reach certain ends; but we ought to realize at the
threshold where the limits of such a technical science lie, as they
are easily overlooked, with resulting confusion. We must understand
that every technical science says only: you must make use of this
means, if you wish to reach this or that particular end. But no
technical science can decide within its limits whether the end itself
is really a desirable one. The technical specialist knows how he ought
to build a bridge or how he ought to pierce a tunnel, presupposing
that the bridge or the tunnel is desired. But whether they are
desirable or not is a question which does not concern the technical
scientist, but which must be considered from economic or political or
other points, of view. Everywhere the engineer must know how to reach
an end, and must leave it to others to settle whether the end in
itself is desirable. Often the end may be a matter of course for every
reasonable being. The extreme case is presented by the applied science
of medicine, where the physician subordinates all his technique to the
end of curing the patient. Yet if we are consistent we must
acknowledge that all his medical knowledge can prescribe to him only
that he proceed in a certain way if the long life of the patient is