mathematics. It is usual with mathematicians, to pretend, that those
ideas, which are their objects, are of so refined and spiritual a nature,
that they fall not under the conception of the fancy, but must be
comprehended by a pure and intellectual view, of which the superior
faculties of the soul are alone capable. The same notion runs through most
parts of philosophy, and is principally made use of to explain oar
abstract ideas, and to shew how we can form an idea of a triangle, for
instance, which shall neither be an isoceles nor scalenum, nor be
confined to any particular length and proportion of sides. It is easy to
see, why philosophers are so fond of this notion of some spiritual and
refined perceptions; since by that means they cover many of their
absurdities, and may refuse to submit to the decisions of clear ideas, by
appealing to such as are obscure and uncertain. But to destroy this
artifice, we need but reflect on that principle so oft insisted on, that
all our ideas are copyed from our impressions. For from thence we may
immediately conclude, that since all impressions are clear and precise,
the ideas, which are copyed from them, must be of the same nature, and
can never, but from our fault, contain any thing so dark and intricate.
An idea is by its very nature weaker and fainter than an impression; but
being in every other respect the same, cannot imply any very great
mystery. If its weakness render it obscure, it is our business to remedy
that defect, as much as possible, by keeping the idea steady and precise;
and till we have done so, it is in vain to pretend to reasoning and
philosophy.



SECT. II. OF PROBABILITY, AND OF THE IDEA OF CAUSE AND EFFECT.