which would permit of the greatest
perfecting (that of the Vertebrates), a plan very different from those
which she has been obliged to form as a preliminary to reaching it, one
understands that, among the multitude of animals, one must necessarily
come across not a single system of organisation which has become
progressively perfected, but diverse very distinct systems, each of
which has come into existence at the moment when each primary organ
first put in its appearance" (p. 171).

For Lamarck this order of Nature was not merely ideal--Nature had
actually formed the classes successively, proceeding from the simpler to
the more complex; she had brought about this evolution by transforming
the primitive species of animals, raising them to higher degrees of
organisation, and modifying them in relation to the environment in which
they found themselves.

Lamarck's theory of evolution is worked out in great detail in his
_Philosophie zoologique_, but the exposition is diffuse and
disconnected; it is better in giving an account of it to follow the more
concise, mature and general exposition which he gives in the
Introduction to his _Histoire naturelle des Animaux sans Vertebres_.[341]
Near the beginning of the Introduction Lamarck gives us in a few short
"Fundamental Principles" the main lines of his general philosophy. He is
a confirmed materialist. Every fact and phenomenon is essentially
physical and owes its existence or production entirely to material
bodies or to relations between them. All change and all movement is in
the last resort due to mechanical causes. Every fact or phenomenon
observed in a living body is at once a physical fact or phenomenon and a
product of organisation (p. 19). Life, thought and sensation are not
properties of matter, but result from particular material combinations.

His thorough-going materialism is most clearly shown in its relation to
living things in the first three of the "Zoological Principles and
Axioms," which are developed further on in the book.

These are as follows:--"1. No kind or particle of matter can have in
itself the power of moving, living, feeling, thinking, nor of having
ideas; and if, outside of man, we observe bodies endowed with all or one
of these faculties, we ought to consider these faculties as physical
phenomena which Nature has been able to produce, not by employing some
particular kind of matter which itself possesses one or other of these
faculties, but