Section 7 of Hume’s An Enquiry concerning Human Understanding evaluates the concept of causation and “necessary connexion.” Hume comes to the conclusion that because human beings are incapable of perceiving the “necessary connexion” in cause and effect relationships, “cause” is nothing but the “idea” or impression of power or action. To illustrate his argument, the philosopher relies on his definitions of (1) impressions (immediate sensory perceptions) and (2) ideas (recollections of impressions that build upon each other and increase in complexity.) Over the course of the section, Hume attempts to prove that no impression exists that would suggest a connection or power between two objects/events. He also formulates two definitions of cause.
Hume’s first premise is that “it is impossible for us to think of anything we have not antecedently felt, either by our external or internal senses.” (102) In other words, without possessing an impression of something man cannot form an idea surrounding it. Hume raises the example of one billiard ball provoking motion in another ball.
While the movement of the second ball consistently follows it’s collision with the first, “there is nothing which can suggest the idea of power.” (103) The mind may observe relationships and action, but the connecting power is imperceptible; cause and effect to a human being are nothing but correlating events. This observation prompts Hume’s second premise that the necessary connection perceived by man is but a “reflection on the operations of our own minds.” (104) Hume turns to the relationship between the mind and body to further destabilize the idea of power. He theorizes that although we are conscious of our will acting on our body, the nature of will itself is again a mystery. Hume lists three truths which undermine the belief that we possess this complete power over the body: (1) the “secret union” between soul and body is unclear, (2) while we may control our limbs the mechanism by which we move them is unknown, and (3) the components within our body such as muscles and nerves, act on their own accord to fulfill our intended movement independent of the mind.
Again, one event follows another, but the essential connection between them remains out of reach. Thus, Hume concludes that the “power” of our mind, or volition, relies on experience rather than an understanding of cause and effect and may vary. Hume devotes Part II to determining a definition of cause, after establishing that a necessary connection is imperceptible to man. Hume concedes that the concept of “cause and effect” is useful in ordering events and attempting to predict the future, although it is based in what man feels only. He proposes two possible definitions of the term that rest on his fourth premise: to man, events are conjoined, rather than connected. The first definition reads, “where if the first object had not been, the second never had existed,” while the second reads, “an object followed by another, and whose appearance always conveys the thought to that other.
” (114) The first definition concerns two entities that consistently correlate, such as one billiard ball moving when being struck by another. Although the necessary connection may not exist, the fact that these two events continually occur together fuses their relationship in man’s mind. Thus, we may say that one causes the other, even though we lack the ability to sense the connection between them; man may predict future happenings with accuracy through observation and experience. The second definition implies that the “mind anticipates the senses” (114) and predicts the effect with accuracy.
Subsequently, the “idea of cause” is resolved. A man that believes that he sees a necessary connection is the product of experience and habit based on impressions that are catalogued as the idea of power/connection/cause in his mind. While these two definitions are equally applicable to cause and effect according to Hume, and accommodate issues surrounding necessary connection, I believe they are vague in application. Hume’s first definition accidentally implies that all events that correlate may be causal. According to the statement “where if the first object had not been, the second never had existed,” two events could occur together once and create an association in the mind.
Furthermore, events that take place together by chance are just as “valid” as those that may very well have the necessary connection, however imperceptible it may be to man. Hume’s second definition similarly promotes delusion. Just as the first implies that events that correlate may be causal, the second relies too heavily on clarity of mind. Not only is the phrase “one object followed by another,” dependent on the first definition, but the second claims that cause and inference are equal. One event when followed by another may denote myriad inferences in individuals, and according to Hume, legitimize a series of causes rather than a single one. While Hume is persuasive in his theory that necessary connection is imperceptible to human beings, his definitions of cause lack the strength of his prior argument.