orbit round the earth, nor the earth in her orbit round the sun,
by a force that varies merely in the inverse ratio of the squares
of the distances. To make the general theory just in application
to the revolutions of these bodies, it was necessary to calculate
accurately the disturbing force of the sun upon the moon, and of
the moon upon the earth; and till these disturbing forces were
properly estimated, actual observations on the motions of these
bodies would have proved that the theory was not accurately true.

I am willing to allow that every voluntary act is preceded by
a decision of the mind, but it is strangely opposite to what I
should conceive to be the just theory upon the subject, and a
palpable contradiction to all experience, to say that the
corporal propensities of man do not act very powerfully, as
disturbing forces, in these decisions. The question, therefore,
does not merely depend upon whether a man may be made to
understand a distinct proposition or be convinced by an
unanswerable argument. A truth may be brought home to his
conviction as a rational being, though he may determine to act
contrary to it, as a compound being. The cravings of hunger, the
love of liquor, the desire of possessing a beautiful woman, will
urge men to actions, of the fatal consequences of which, to the
general interests of society, they are perfectly well convinced,
even at the very time they commit them. Remove their bodily
cravings, and they would not hesitate a moment in determining
against such actions. Ask them their opinion of the same conduct
in another person, and they would immediately reprobate it. But
in their own case, and under all the circumstances of their
situation with these bodily cravings, the decision of the
compound being is different from the conviction of the rational