the matter. Evolution is in reality nothing but a great induction,
which we are compelled to make by the comparative study of the most
important facts of morphology and physiology. But we must draw our
conclusion according to the laws of induction, and not attempt to
determine scientific truths by direct measurement and mathematical
calculation. In the study of living things we can scarcely ever
directly and fully, and with mathematical accuracy, determine the
nature of phenomena, as is done in the simpler study of the inorganic
world--in chemistry, physics, mineralogy, and astronomy. In the
latter, especially, we can always use the simplest and absolutely
safest method--that of mathematical determination. But in biology this
is quite impossible for various reasons; one very obvious reason being
that most of the facts of the science are very complicated and much
too intricate to allow a direct mathematical analysis. The greater
part of the phenomena that biology deals with are complicated
HISTORICAL PROCESSES, which are related to a far-reaching past, and as
a rule can only be approximately estimated. Hence we have to proceed
by INDUCTION--that is to say, to draw general conclusions, stage by
stage, and with proportionate confidence, from the accumulation of
detailed observations. These inductive conclusions cannot command
absolute confidence, like mathematical axioms; but they approach the
truth, and gain increasing probability, in proportion as we extend the
basis of observed facts on which we build. The importance of these
inductive laws is not diminished from the circumstance that they are
looked upon merely as temporary acquisitions of science, and may be
improved to any extent in the progress of scientific knowledge. The
same may be said of the attainments of many other sciences, such as
geology or archeology. However much they may be altered and improved
in detail in the course of time, these inductive truths may retain
their substance unchanged.