BOOK I PART II
senses, than the distinction betwixt a curve and
a right line; nor are there any ideas we more
easily form than the ideas of these objects. But
however easily we may form these ideas, it is
impossible to produce any definition of them,
which will fix the precise boundaries betwixt
them. When we draw lines upon paper, or any
continued surface, there is a certain order, by
which the lines run along from one point to
another, that they may produce the entire im-
pression of a curve or right line; but this order
is perfectly unknown, and nothing is observed
but the united appearance. Thus even upon the
system of indivisible points, we can only form
a distant notion of some unknown standard to
these objects. Upon that of infinite divisibility
we cannot go even this length; but are reduced
meerly to the general appearance, as the rule
by which we determine lines to be either curve