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,

First, That they can be set down and represented by sensible marks,
which have a greater and nearer correspondence with them than any words
or sounds whatsoever. Diagrams drawn on paper are copies of the ideas in
the mind, and not liable to the uncertainty that words carry in their
signification. An angle, circle, or square, drawn in lines, lies open to
the view, and cannot be mistaken: it remains unchangeable, and may at
leisure be considered and examined, and the demonstration be revised,
and all the parts of it may be gone over more than once, without any
danger of the least change in the ideas. This cannot be thus done in
moral ideas: we have no sensible marks that resemble them, whereby we
can set them down; we have nothing but words to express them by; which,
though when written they remain the same, yet the ideas they stand for
may change in the same man; and it is very seldom that they are not
different in different persons.

Secondly, Another thing that makes the greater difficulty in ethics is,
That moral ideas are commonly more complex than those of the
figures ordinarily considered in mathematics. From whence these two
inconveniences follow:--First, that their names are of more uncertain
signification, the precise collection of simple ideas they stand for
not being so easily agreed on; and so the sign that is used for them in
communication always, and in thinking often, does not steadily carry
with it the same idea. Upon which the same disorder, confusion, and
error follow, as would if a man, going to demonstrate something of an
heptagon, should, in the diagram he took to do it, leave out one of the
angles, or