s we form neither affect our existence nor our welfare;
and we are not forced by any physical necessity to correct them.
Imagination, on the contrary, which is ever wandering beyond the bounds
of truth, joined to self-love and that self-confidence we are so apt to
indulge, prompt us to draw conclusions which are not immediately derived
from facts; so that we become in some measure interested in deceiving
ourselves. Hence it is by no means to be wondered, that, in the science
of physics in general, men have often made suppositions, instead of
forming conclusions. These suppositions, handed down from one age to
another, acquire additional weight from the authorities by which they
are supported, till at last they are received, even by men of genius, as
fundamental truths.

The only method of preventing such errors from taking place, and of
correcting them when formed, is to restrain and simplify our reasoning
as much as possible. This depends entirely upon ourselves, and the
neglect of it is the only source of our mistakes. We must trust to
nothing but facts: These are presented to us by Nature, and cannot
deceive. We ought, in every instance, to submit our reasoning to the
test of experiment, and never to search for truth but by the natural
road of experiment and observation. Thus mathematicians obtain the
solution of a problem by the mere arrangement of data, and by reducing
their reasoning to such simple steps, to conclusions so very obvious, as
never to lose sight of the evidence which guides them.

Thoroughly convinced of these truths, I have imposed upon myself, as a
law, never to advance but from what is known to what is unknown; never
to form any conclusion which is not an immediate consequence necessarily
flowing from observation and experiment; and always to arrange the
facts, and the conclusions which are drawn from them, in such an order
as shall render it most easy for beginners in the study of chemistry
thoroughly to understand them. Hence I have been obliged to depart from
the usual order of courses of lectures and of treatises upon chemistry,
which always assume the first principles of the science, as known, when
the pupil or the reader should never be supposed to know them till they
have been explained in subsequent lessons. In almost every instance,
these begin by treating of the elements of matter, and by explaining the
table of affinities, without considering, that, in so doing, they must
bring the pri