solutely particular: for we cannot perceive
anything without classing it, more or less definitely, with things
already known to us; nor describe it without using connotative terms
which imply a classification of the things denoted. Still, we may
consider an observation as particular, in comparison with a law that
includes it with numerous others in one general proposition. To turn an
observation into an experiment, or (where experiment is impracticable)
to repeat it with all possible precautions and exactness, and to
describe it as to the duration, quantity, quality and order of
occurrence of its phenomena, is the first stage of scientific
manufacture. Then comes the formulation of an empirical law; and lastly,
if possible, deduction or derivation, either from higher laws previously
ascertained, or from an hypothesis. However, as a word is used in
various senses, we often speak of laws as 'facts': we say the law of
gravitation is a fact, meaning that it is real, or verifiable by
observations or experiments.

Sec. 2. Secondary Laws may also be classified according to their constancy
into--(1) the Invariable (as far as experience reaches), and (2)
Approximate Generalisations in the form--Most X's are Y. Of the
invariable we have given examples above. The following are approximate
generalisations: Most comets go round the Sun from East to West; Most
metals are solid at ordinary temperatures; Most marsupials are
Australasian; Most arctic animals are white in winter; Most cases of
plague are fatal; Most men think first of their own interests. Some of
these laws are empirical, as that 'Most metals are solid at ordinary
temperatures': at present no reason can be given for this; nor do we
know why most cases of plague are fatal. Others, however, are at least
partially derivative, as that 'Most arctic animals are white'; for this
seems to be due to the advantage of concealment in the snow; whether, as
with the bear, the better to surprise its prey, or, with the hare, to
escape the notice of its enemies.

But the scientific treatment of such a proposition requires that we
should also explain the exceptions: if 'Most are,' this implies that
'Some are not'; why not, then? Now, if we can give reasons for all the
exceptions, the approximate generalisation may be converted into an
universal one, thus: 'All arctic animals are white, unless (like the
raven) they need no concealment either to prey or to escape; or unless
mutual recogni