An Essay Concerning Humane Understanding, Volume 2: MDCXC, Based on the 2nd Edition, Books 3 and 4
John Locke · en
The idea of a supreme Being, infinite in power, goodness, and wisdom,
whose workmanship we are, and on whom we depend; and the idea of
ourselves, as understanding, rational creatures, being such as are clear
in us, would, I suppose, if duly considered and pursued, afford such
foundations of our duty and rules of action as might place MORALITY
amongst the SCIENCES CAPABLE OF DEMONSTRATION: wherein I doubt not
but from self-evident propositions, by necessary consequences, as
incontestible as those in mathematics, the measures of right and wrong
might be made out, to any one that will apply himself with the same
indifferency and attention to the one as he does to the other of these
sciences. The RELATION of other MODES may certainly be perceived, as
well as those of number and extension: and I cannot see why they should
not also be capable of demonstration, if due methods were thought on to
examine or pursue their agreement or disagreement. 'Where there is no
property there is no injustice,' is a proposition as certain as any
demonstration in Euclid: for the idea of property being a right to
anything, and the idea of which the name 'injustice' is given being the
invasion or violation of that right, it is evident that these ideas,
being thus established, and these names annexed to them, I can as
certainly know this proposition to be true, as that a triangle has three
angles equal to two right ones. Again: 'No government allows absolute
liberty.' The idea of government being the establishment of society upon
certain rules or laws which require conformity to them; and the idea of
absolute liberty being for any one to do whatever he pleases; I am as
capable of being certain of the truth of this proposition as of any in
the mathematics.
19. Two things have made moral Ideas to be thought incapable of
Demonstration: their unfitness for sensible representation, and their
complexedness.
That which in this respect has given the advantage to the ideas
of quantity, and made them thought more capable of certainty and
demonstration, is,