anguage and ideas are
concerned, it matters not whether the sun actually _sinks_ behind the
hills, or the hills interpose between it and us; whether the landscape
_recedes_ from our view, or the shades of night intercept so as to
obscure our vision. The habit of thought is the same, and the form of
expression must agree with it. We say the sun _rises_ and _sets_, in
reference to the obvious fact, without stopping to inquire whether it
really moves or not. Nor is such an inquiry at all necessary, as to
matter of fact, for all we mean by such expressions, is, that by some
process, immaterial to the case in hand, the sun stands in a new
relation to the earth, its altitude is elevated or depressed, and hence
the action is strictly relative. For we should remember that _rising_
and _setting_, _up_ and _down_, _above_ and _below_, in reference to the
earth, are only relative terms.

We speak and read of the _changes_ of the moon, and we correctly
understand each other. But in truth the moon changes no more at one time
than at another. The action is purely relative. One day we observe it
_before_ the sun, and the next _behind_ it, as we understand these
terms. The precise time of the change, when it will appear to us in a
different relation to the sun, is computed by astronomers, and set down
in our almanacs; but it changes no more at that time than at any other,
for like every thing else, it is _always changing_.

In a case we mentioned in a former lecture, "John _looks_ like or
_resembles_ his brother," we have an example of relative action. So in
the case of two men travelling the same way, starting together, but
advancing at different rates; one, we say, _falls_ behind the other. In
this manner of expression, we follow exactly the principles on which we
started, and suit our language to our ideas and habits of thinking. By
the law of optics things are reflected upon the retina of the eye
inversely, that is, upside down; but they are always seen in a proper
relation to each other, and if there is any thing wrong in the case, it
is overcome by early habit; and so our language accords with things as
they are manifested to our understandings.

These examples will serve to illustrate what we mean by relative action,
when applied to natural philosophy or the construction of language.

I had intended in this lecture to have treated of the agents and objects
of verbs, to prove, in accordance with the first and closest principle