10 THE SOCIAL THEORY OF GEORG SIMMEL 
objective truth, there would result an irreconcilable con- 
flict and mutual negation; but in the form of alternation 
an organic unity is possible. Each of them becomes then 
merely a heuristic principle, that is, each will have to 
search for a foundation and a justification at every point 
of its application. In this way every exact science has to 
submit to an investigation of its presuppositions, and 
these presuppositions themselves will have to be submitted 
to a psychological and historical investigation. 
This mutual dependence of the two methods is also 
manifest in the most general opposition within our knowl- 
edge, the opposition between what is a priori and what is 
experience. All experience results from an active, forma- 
tive functioning of the mind on the immediate sense im- 
pressions, and it is only through this transformation that 
the immediate data of experience become knowedge. But 
the certainty that there are such a priori thought forms 
is not accompanied by the certainty of what they are. 
What has been accepted as an a priori form at one time 
has been proven to be an empirical and historical struc- 
ture at a later time. Not only are the a priori categories 
not permanently fixed and static, but what is empirically 
obtained in one field of inquiry may function as a priori 
for another field of inquiry. A complete understanding of 
experience involves, therefore, the double task of finding 
the aprioristic norms which shape it and of tracing for each 
single a priori its genetic growth out of former experience. 
Each of these two methods still contains something sub- 
jective, but in the form of a mutual determination they 
can picture that which we call objectivity. 
The great advantage of this relativistic over other 
epistemological doctrines is that it does not need to ask 
for exemption from application to itself. The doctrine is 
not destroyed by the fact that it is itself relativistic.