ness on the idea;
and the examination of the idea bestows a like clearness on all our
reasoning.

Let us therefore cast our eye on any two objects, which we call
cause and effect, and turn them on all sides, in order to find that
impression, which produces an idea, of such prodigious consequence.
At first sight I perceive, that I must not search for it in any of
the particular qualities of the objects; since which-ever of these
qualities I pitch on, I find some object, that is not possessed of it,
and yet falls under the denomination of cause or effect. And indeed
there is nothing existent, either externally or internally, which is
not to be considered either as a cause or an effect; though it is plain
there is no one quality, which universally belongs to all beings, and
gives them a title to that denomination.

The idea, then, of causation must be derived from some relation among
objects; and that relation we must now endeavour to discover. I find
in the first place, that whatever objects are considered as causes
or effects, are contiguous; and that nothing can operate in a time or
place, which is ever so little removed from those of its existence.
Though distant objects may sometimes seem productive of each other, they
are commonly found upon examination to be linked by a chain of causes,
which are contiguous among themselves, and to the distant objects; and
when in any particular instance we cannot discover this connexion, we
still presume it to exist. We may therefore consider the relation of
CONTIGUITY as essential to that of causation; at least may suppose it
such, according to the general opinion, till we can find a more [Part
IV. Sect. 5.] proper occasion to clear up this matter, by examining what
objects are or are not susceptible of juxtaposition and conjunction.

The second relation I shall observe as essential to causes and effects,
is not so universally acknowledged, but is liable to some controversy.
It is that of PRIORITY Of time in the cause before the effect. Some
pretend that it is not absolutely necessary a cause should precede its
effect; but that any object or action, in the very first moment of its
existence, may exert its productive quality, and give rise to another
object or action, perfectly co-temporary with itself. But beside that
experience in most instances seems to contradict this opinion, we may
establish the relation of priority by a kind of inference or reasoning.
It is an established