general or universal motion, and that it thus
falls under the same head as other motions, either those which originate
in ourselves and are propagated from our bodies to external objects, or
those which, springing from an unknown beginning, are for ever
continuing as before.

This then is the answer to the question, Why do we believe in the
uniformity of Nature? We believe in it because we find it so. Millions
on millions of observations concur in exhibiting this uniformity. And
the longer our observation of Nature goes on, the greater do we find the
extent of it. Things that once seemed irregular are now known to be
regular. Things that seemed inexplicable on this hypothesis are now
explained. Every day seems to add not merely to the instances but to
the wide-ranging classes of phenomena that come under the rule. We had
reason long ago to hold that the quantity of matter was invariable. We
now have reason to think that the quantity of force acting on matter is
invariable. And to this is to be added the evidence of scientific
prediction, the range of which is perpetually increasing, and which
would be obviously impossible if Nature were not uniform. And yet again
to this is to be added that this uniformity does not consist in a vast
number of separate and independent laws, but that these laws already
form a system with one another, and that that system is daily becoming
more complete. We believe in the uniformity of Nature because, as far as
we can observe it, that is the character of Nature.

And I use the word character on purpose, because it indicates better
than any other word that I could find at once the nature and limitation
of our belief.

For, if the origin of this belief be what I have described, it is
perfectly clear that, however vast may be the evidence to prove this
uniformity, the conclusion can never go beyond the limits of this
evidence, and generality can never be confounded with universality. The
certainty that Nature is uniform is not at all, and never can be, a
certainty of the same kind as the certainty that four times five are
twenty.

We can assert that the general character of Nature is uniformity, but we
cannot go beyond this. Every separate law of nature is established by
induction from the facts, and so too is the general uniformity. Every
separate law of Nature is a working hypothesis. So too is the uniformity
of Nature a working hypothesis, and it never can be more. It is true
that the