pothesis and the observed phenomena of light is the chief part of the
verification; which has now been so successfully accomplished that we
generally hear of the 'Undulatory Theory.' Sometimes a new agent only is
proposed; as the planet Neptune was at first assumed to exist in order
to account for perturbations in the movements of Uranus, influencing it
according to the already established law of gravitation. Sometimes the
agents are known, and only the law of their operation is hypothetical,
as was at first the case with the law of gravitation itself. For the
agents, namely, Earth, falling bodies on the Earth, Moon, Sun, and
planets were manifest; and the hypothesis was that their motions might
be due to their attracting one another with a force inversely
proportional to the squares of the distances between them. In the
Ptolemaic Astronomy, again, there was an hypothesis as to the
collocation of the heavenly bodies (namely, that our Earth was the
centre of the universe, and that Moon, Sun, planets and stars revolved
around her): in the early form of the system there was also an
hypothesis concerning agents upon which this arrangement depended
(namely, the crystalline spheres in which the heavenly bodies were
fixed, though these were afterwards declared to be imaginary); and an
hypothesis concerning the law of operation (namely, that circular motion
is the most perfect and eternal, and therefore proper to celestial
things).

Hypotheses are by no means confined to the physical sciences: we all
make them freely in private life. In searching for anything, we guess
where it may be before going to look for it: the search for the North
Pole was likewise guided by hypotheses how best to get there. In
estimating the characters or explaining the conduct of acquaintances or
of public men, we frame hypotheses as to their dispositions and
principles. 'That we should not impute motives' is a peculiarly absurd
maxim, as there is no other way of understanding human life. To impute
bad motives, indeed, when good are just as probable, is to be wanting in
the scientific spirit, which views every subject in 'a dry light.' Nor
can we help 'judging others by ourselves'; for self-knowledge is the
only possible starting-point when we set out to interpret the lives of
others. But to understand the manifold combinations of which the
elements of character are susceptible, and how these are determined by
the breeding of race or family under vario