I believe it will not be necessary to employ many words in shewing the weakness of this argument, after what I have said of the foregoing.  They are all of them founded on the same fallacy, and are derived from the same turn of thought.  It is sufficient only to observe, that when we exclude all causes we really do exclude them, and neither suppose nothing nor the object itself to be the causes of the existence; and consequently can draw no argument from the absurdity of these suppositions to prove the absurdity of that exclusion.  If every thing must have a cause, it follows, that upon the exclusion of other causes we must accept of the object itself or of nothing as causes.  But it is the very point in question, whether every thing must have a cause or not; and therefore, according to all just reasoning, it ought never to be taken for granted.

They are still more frivolous, who say, that every effect must have a, cause, because it is implyed in the very idea of effect.  Every effect necessarily pre-supposes a cause; effect being a relative term, of which cause is the correlative.  But this does not prove, that every being must be preceded by a cause; no more than it follows, because every husband must have a wife, that therefore every man must be marryed.  The true state of the question is, whether every object, which begins to exist, must owe its existence to a cause:  and this I assert neither to be intuitively nor demonstratively certain, and hope to have proved it sufficiently by the foregoing arguments.

Since it is not from knowledge or any scientific reasoning, that we derive the opinion of the necessity of a cause to every new production, that opinion must necessarily arise from observation and experience.  The next question, then, should naturally be, how experience gives rise to such a principle?  But as I find it will be more convenient to sink this question in the following, Why we conclude, that such particular causes must necessarily have such particular erects, and why we form an inference from one to another? we shall make that the subject of our future enquiry.  It will, perhaps, be found in the end, that the same answer will serve for both questions.

SECT.  IV.  OF THE COMPONENT PARTS OF OUR REASONINGS CONCERNING CAUSE AND EFFECT.

Though the mind in its reasonings from causes or effects carries its view beyond those objects, which it sees or remembers, it must never lose sight of them entirely, nor reason merely upon its own ideas, without some mixture of impressions, or at least of ideas of the memory, which are equivalent to impressions.  When we infer effects from causes, we must establish the existence of these causes; which we have only two ways of doing, either by an immediate perception of our memory or senses, or by an inference from other causes; which causes again we must ascertain in the same manner, either by a present impression, or by an inference from their causes, and so on, till we arrive at some object, which we see or remember.  It is impossible for us to carry on our inferences in infinitum; and the only thing, that can stop them, is an impression of the memory or senses, beyond which there is no room for doubt or enquiry.