ionalistic edifice
contradicts the sensationalistic foundation. Locke had hoped to show the
value and the limits of knowledge by an inquiry into the origin of ideas,
but his estimate of this value and these limits cannot be proved from the
_a posteriori_ origin of ideas--it can only be maintained in despite of
this, and stands in need of support from some (rationalistic) principle
elsewhere obtained. Thinkers who trace back all simple ideas to outer and
inner perception we expect to reject every attempt to extend knowledge
beyond the sphere of experience, to declare the combinations of ideas
which have their origin in sensation trustworthy, and those which are
formed without regard to perception, illusory; or else, with Protagoras,
to limit knowledge to the individual perceiving subject, with a consequent
complete denial of its general validity. But exactly the opposite of all
these is found in Locke. The remarkable spectacle is presented of a
philosopher who admits no other sources of ideas than perception and the
voluntary combination of perceptions, transcending the limits of experience
with proofs of the divine existence, viewing with suspicion the ideas of
substance formed at the instance of experience, and reducing natural
science to the sphere of mere opinion; while, on the other hand, he
ascribes reality and eternal validity to the combinations of ideas formed
independently of perception, which are employed by mathematics and ethics,
and completely abandons the individualistic position in his naive faith in
the impregnable validity of the relations of ideas, which is evident to all
who turn their attention to them. The ground for the universal validity of
the relations among ideas as well as of our knowledge of them, naturally
lies not in their empirical origin (for my experience gives information to
me alone, and that only concerning the particular case in question), but in
the uniformity of man's rational constitution. If two men really have the
same ideas--not merely think they have because they use similar
language--it is impossible, according to Locke, that they should hold
different opinions concerning the relation of their ideas. With this
conviction, that the universal validity of knowledge is rooted in the
uniformity of man's rational constitution, and the further one, that we
attain certain knowledge only when things conform to our ideas, Locke
closely approaches Kant; while his assumption of a fixed orde