this theory, the instinctive and spontaneous belief in
"causation" is not extinguished nor even impaired; but that they seek
merely _to substitute "laws" for "causes_," or rather to represent _the
laws of nature_ as the only _efficient causes_ of all natural phenomena.
They thus identify or confound two things which it is of the utmost
consequence to discriminate and keep distinct. There is an ambiguity,
however, in the common usage of the term "law," which may seem to give a
plausible appearance to their theory, or at least to vail over and
conceal its radical fallacy. It denotes sometimes the mere statement of
_a general fact_, or the result of a comprehensive generalization,
founded on the observation and comparison of many particular facts; it
denotes at other times _the force or power_, whatever that may be, which
produces any given set of phenomena. The "law" of gravitation, for
example, is often used to denote nothing more than the _general fact_,
ascertained by experience, that all bodies near the surface of the earth
tend to its centre with a velocity proportioned directly to their mass,
and inversely to the square of their distance; and when it is employed
in _this_ sense, it determines nothing as to the "cause" which is in
operation,--it affirms merely a fact, or a fact reduced to a formula,
and confirmed by universal experience. But it is often transferred, at
least mentally and almost perhaps unconsciously, to denote some "power"
which is instinctively supposed to be in operation when any change is
observed,--a "power" which may be conceived of, either as a _property_
inherent in mind or in matter, or as a _force_, such as the Divine
volition, acting upon it _ab extra_; and it is only in the latter of
these two senses, as denoting a "cause," properly so called, and not a
mere fact or law, that it can be applied to account for any phenomenon.
In like manner, the "laws of motion" are merely the generalized results
of our experience and observation relative to the direction, velocity,
and other phenomena of moving bodies; but "motion," although it is
regulated, is not produced, by these laws; it depends on a "cause,"
whatever that may be, which is not only distinguishable, but different
from them all. Yet when we speak of the "laws of motion," we may
imperceptibly include, in our conception of them, that _force_ or
_power_ which impels the body, as well as the mere _law_ or _rule_ which
regulates its movements.