present testimony of our senses, or the
records of our memory. All reasonings concerning matter of fact seem to
be founded on the relation of _cause_ and _effect_. If we would satisfy
ourselves, therefore, concerning the nature of that evidence which
assures us of matters of fact, we must inquire how we arrive at the
knowledge of cause and effect.

I shall venture to affirm, as a general proposition which admits of no
exception, that the knowledge of this relation is not, in any instance,
attained by reasonings _a priori_, but arises entirely from experience.

To convince us that all the laws of nature, and all the operations of
bodies without exception, are known only by experience, the following
reflections may perhaps suffice. Were any object presented to us, and
were we required to pronounce concerning the effect which will result
from it, without consulting past observation, after what manner, I
beseech you, must the mind proceed in this operation? It must invent or
imagine some event, which it ascribes to the object as its effect; and
it is plain that this invention must be entirely arbitrary. The mind can
never possibly find the effect in the supposed cause by the most
accurate scrutiny and examination. For the effect is totally different
from the cause, and, consequently, can never be discovered in it.

A stone or piece of metal raised into the air and left without any
support immediately falls. But, to consider the matter _a priori_, is
there anything we discover in this situation which can beget the idea of
a downward rather than an upward, or any other motion, in the stone or
metal?

In a word, then, every effect is a distinct event from its cause. It
could not, therefore, be discovered in the cause, and the first
invention or conception of it, _a priori_, must be entirely arbitrary.
And, even after it is suggested, the conjunction of it with the cause
must appear equally arbitrary, since there are always many other effects
which to reason must seem fully as consistent and natural. In vain,
therefore, should we pretend to determine any single event, or infer any
cause or effect, without the assistance of observation and experience.

Hence, we may discover the reason why no philosopher who is rational and
modest has ever pretended to assign the ultimate cause of any natural
operation, or to show distinctly the action of that power which produces
any single effect in the universe.

I say, then, that even