David Hume makes a strong affirmation in section IV of an Enquiry Concerning Human Understanding. Hume states, “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 entirely from experience.”In this statement, when discussing “knowledge of this relation,” Hume is referring to the relation between cause and effect. This argument can easily be dismissed as skeptical, for it puts all knowledge of this sort in doubt. However, Hume does not hastily doubt that this knowledge is not a priori, as a skeptic would. Instead Hume offers a sound argument as to why cause and effect knowledge can not be a priori, and thus his argument is not skeptical at all.
Before Hume commits himself to this affirmation, he establishes several things first. He explains that all reasonings concerning matter of fact are founded on the relation of Cause and Effect. In support of this, Hume explains that, if asked, any man believing in a matter of fact would give as a reason in support of this fact, some other fact. It is from this that Hume concludes that all reasonings concerning fact are of the same nature. It is here that one continually assumes that there is a connection between the current fact and that, which is inferred from it. Furthermore, Hume states where there nothing to bind them together; the inference would be entirely precarious.Meaning, any matter of fact is supported only by another matter of fact, and if this connection is removed, one is left with a fact that is completely dependent. In addition, any fact will ultimately be dependent on a primary fact, which in turn is founded on cause and effect. It is only after Hume establishes this that he affirms that knowledge of this relation is never attained by reasonings a priori.
Knowledge based on cause and effect, for Hume, relies entirely on human experience, and it is for this reason that it can not be a priori. Hume does not blindly state this proposition, he supports it with several examples that I find irrefutable. He suggests that no man when presented with gunpowder can imagine the explosion that can follow. The same is true when discussing the consequences of releasing a stone from ones hand. Without prior knowledge, it would be impossible to predict that the stone would fall to the ground. “No object ever discovers, by the qualities that which appear to the senses, either causes which produced it, or the effects which will arise from it; nor can our reason, unassisted by experience, ever draw any inference concerning real existence and matter of fact.”It is here that Hume proves that knowledge based on cause and effect relies solely on experience and can not be based on reasonings a priori.
Knowledge that is a priori is the exact opposite of knowledge that is obtained through experience. For the very definition of a priori is knowledge that is presupposed as prior to experience. It is apparent, from Humes past arguments that certain things are impossible to know prior to experience. Hume applies this same reasoning to all the laws of nature, and all the operations of bodies. He states that it is the influence of custom to infer that anyone without prior knowledge, would be able to predict the communication of motion between one Billiard-ball to another upon impulse. Hume follows by stating, “were any object presented to us, and were we required to pronounce concerning the effect, which would result from it, it would be impossible to do so, without consulting past observation.”In all aspects of matter of fact, Hume has provided sufficient evidence, to support his affirmation.
A skeptical argument is one in which everything is doubted. Hume is certainly not doubting everything when affirms that knowledge relating to cause and effect is never a priori. For it is in this same affirmation that he offers an alternate explanation to knowledge of this relation. Instead of solely doubting, as a skeptic would, Hume offers experience as an alternate explanation to the relation between matters of fact. While Hume does deny that knowledge of the relation between cause and effect is a priori, he is far from skeptical. He instead gives a complete and sound argument as to why this knowledge is based on experience instead. It is for this reason that his argument is not a skeptical on.
Hume, David, An Enquiry Concerning Human Understanding