t
that what was a part of the object, heavier-things-pushing-their
way-through-soil-of-lighter-texture, can become a mere idea. Earlier it
was an object. Until it could be tested the earthworm as the cause of
the disappearance of the dressings was also Darwin's idea. It became
fact. For science at least it is quite impossible to distinguish between
what in an object must be fact and what may be idea. The distinction
when it is made is dependent upon the form of the problem and is
functional to its solution, not metaphysical. So little can a consistent
line of cleavage between facts and ideas be indicated, that we can
never tell where in our world of observation the problem of science will
arise, or what will be regarded as structure of reality or what
erroneous idea.

There is a strong temptation to lodge these supposititious
fact-structures in a world of conceptual objects, molecules, atoms,
electrons, and the like. For these at least lie beyond the range of
perception by their very definition. They seem to be in a realm of
things-in-themselves. Yet they also are found now in the field of
fact and now in that of ideas. Furthermore, a study of their structure
as they exist in the world of constructive science shows that
their infra-sensible character is due simply to the nature of our
sense-processes, not to a different metaphysical nature. They occupy
space, have measurable dimensions, mass, and are subject to the same
laws of motion as are sensible objects. We even bring them indirectly
into the field of vision and photograph their paths of motion.

The ultimate elements referred to above provide a consistent symbolism
for the finding and formulating of applied mathematical sciences, within
which lies the whole field of physics, including Euclidian geometry as
well. However, they have succeeded in providing nothing more than a
language and logic pruned of the obstinate contradictions, inaccuracies,
and unanalyzed sensuous stuff of earlier mathematical science. Such a
rationalistic doctrine can never present in an unchanged form the
objects with which natural science deals in any of the stages of its
investigation. It can deal only with ultimate elements and forms of
propositions. It is compelled to fall back on a theory of analysis
which reaches ultimate elements and an assumption of inference as an
indefinable. Such an analysis is actually impossible either in the field
of the conceptual objects into which physical