he experiments of
Chemistry, and the art of Navigation. When the aeronaut inflates his
balloon with a gas specifically lighter than atmospheric air, or the
ship-builder constructs vessels of wood or iron, so that when filled
with air they shall be lighter than water, and float with their cargo on
its surface, each is attempting to counteract the law of gravitation by
the application of certain other related laws: but no one ever dreams of
their _disobeying_ God in thus availing themselves of one physical agent
to counterpoise another. The "moral law," however, cannot be treated in
the same way, and that simply because it is generically different.

It is true, that _indirectly_ the laws of Nature, when known, may and
ought to regulate our practical conduct; not, however, by virtue of any
obligation imposed _by them_ on our conscience, but solely by virtue of
that law of _moral prudence_ which springs from conscience itself, and
which teaches us that we _ought_ so to act with reference to outward
objects as to secure, so far as we can, our own safety and happiness,
and the welfare of our fellow-men. But there can be no greater blunder
than to confound _the laws of natural objects_ with _the law of human
conduct_; and into this deplorable blunder Mr. Combe has allowed himself
to fall. Throughout the whole of his statements respecting the "natural
laws," there are two things included under one name, which are perfectly
distinct and separate from each other. In the first place, there are the
laws which belong to the constitution of natural objects, and which
regulate their mutual action on one another: in the second place, there
are, in the words of a late sagacious layman, "_rules_ which the
intellect of man is able to deduce for the regulation of his own
conduct, by means of his knowledge of those laws which govern the
phenomena of Nature. These last are perfectly distinct from the former;
and it is a monstrous confusion of ideas to mix them up together....
The true state of the case is this,--it is for our interest to study
these natural arrangements, and to accommodate our conduct to them, as
far as we know them; and in doing so, we _obey_, not those laws of
Nature, physical and organic, but the laws of _prudence and good sense_,
arising from a due use of our moral and intellectual faculties."[199]
Another acute writer,[200] who states the substance of the argument in
very few words, has shown that the theory of "natural