theses. From a positivistic point of view, however, the goal is not
only practically unattainable, but it is irrational, for there seems to
be every evidence that it expresses something contrary to the nature of
the real. Yet scientific theory is not wholly arbitrary. We cannot
construe nature as constituted of any sorts of entities that may suit
our whim. And this is because science itself recognizes that its
entities are not really isolated, but are endowed with all sorts of
properties that serve to connect them with other entities. They are only
symbols of critical points of reality which, conceived in a certain way,
make the behavior of the whole intelligible. Indeed, the only
significant sense in which they are true for the scientist is that they
indicate real connections that might otherwise have been overlooked, and
this is only possible from the fact that reality has the characteristics
that they present and that, with their relations, they give an
approximate presentation of what is actually presented just as a
successful portrait painter considers the individuality of the eyes,
nose, mouth, etc., although he does not imply that a face is compounded
of these separate features as a house is built of boards.

The atomic theory, for example, has undoubtedly been of the greatest
service to chemistry, and atoms undoubtedly denote a significant
resting-place in the analysis of the physical world. Yet in the light of
electron theories, it is becoming more and more evident that atoms are
not ultimate particles, and are not even all alike (Becker, "Isostasy
and Radioactivity," _Sci._, Jan. 29, 1915) when they represent a single
substance. Again, while there is as yet no evidence to suggest that the
electron must itself be considered as divisible (unless it be the
distinction between the positive and negative electron), there are
suggestions that electrons may themselves arise and pass away (cf.
Moore, _Origin, and Nature of Life_, p. 39). "A wisely positivistic
mind," writes Enriques (_Problems of Science_, p. 34), "can see in the
atomic hypothesis only a subjective representation,"[34] and, we might
add, "in any other hypothesis." He continues (pp. 34-36): "robbing the
atom of the concrete attributes inherent in its image, we find ourselves
regarding it as a mere symbol. The logical value of the atomic theory
depends, then, upon the establishment of a proper correspondence between
the symbols which it contains and the r