policy for the selection of laborers is the ideal one. He is confined
to the statement; if you wish this end, then you must proceed in this
way; but it is left to you to express your preference among the ends.
Applied psychology can, therefore, speak the language of an exact
science in its own field, independent of economic opinions and
debatable partisan interests. This is necessary limitation, but in
this limitation lies the strength of the new science. The psychologist
may show how a special commodity can be advertised; but whether from a
social point of view it is desirable to reinforce the sale of these
goods is no problem for psychotechnics. If a sociologist insists that
it would be better if not so many useless goods were bought, and that
the aim ought rather to be to protect the buyer than to help the
seller, the psychologist would not object. His interest would only be
to find the right psychological means to lead to this other social
end. He is partisan neither of the salesman nor of the customer,
neither of the capitalist nor of the laborer, he is neither Socialist
nor anti-Socialist, neither high-tariff man nor free-trader. Here,
too, of course, there are certain goals which are acknowledged on all
sides, and which therefore hardly need any discussion, just as in the
case of the physician, where the prolongation of life is practically
acknowledged as a desirable end by every one. But everywhere where the
aim is not perfectly a matter of course, the psychotechnical
specialist fulfills his task only when he is satisfied with
demonstrating that certain psychical means serve a certain end, and
that they ought to be applied as soon as that end is accepted.

The whole system of psychotechnical knowledge might be subdivided
under either of the two aspects. Either we might start from the
various mental processes and ask for what end each mental factor can
be practically useful and important, or we can begin with studying