According to the Weltanschauung associated wlth the epistemology of complexity,
the history of the Universe proceeds from lower levels of complexity to higher and
higher ones -- from elementary particles to atoms, molecules, life. At each level
new concepts and laws apply bccause new properties of the objective reality emerge.

The body of science is therefore seen as a collection of different disciplines,
each pertaining to a particular level of complexity. They are all founded on
general physics, which has a special status because it is concerned with the
ultimate constituents and laws of the physical world, but do not reduce to it,
because each of them has what makes it an intdependent field of inquiry. According
to the new conception of science and Nature thus defined, chemistry has the task of
looking at matter by trying to trace back its properties to the properties of the
entities characteristic of the lowest level where new aspects of reality due to
complexity appear, viz. molecules.

This is justified by the consideration that chemistry differs from the branches
of science in that it is the science of compound substances insofar as tbey are
compound; that is to say, by virtue of the acknowledged correspondence between
compound substances and molecular species, it is the science of molecules insofar as
they are molecules, The limitation "insofar as" with reference to molecules is
required to specify that, although the general notion of molecule can easily be
appropriated by other sciences - for chemists a molecule is characterized by
molecular structure.

Since knowledge of molecular reality is knowledge of the simplest level of
complexity, cbemistry deserves the status of the reference science for philosophers of
science and of Nature when engaged in reflections on complexity.