Vygotsky appears to draw heavily on
Münsterberg's ideas about unification in practices as the requirement for
uniting the two kinds of psychology Münsterberg (1914):" Unification is
reached in applied psychology which speaks of the practical application of
mental facts in the service of human purposes. The selection of these purposes
is a matter of purposive psychology, the mental effects to be used a matter of
causal psychology. They are thus joined in that practical part which comes
nearest to real life (p. 16)."