Hume’s Explanation of Cause and Effect

In David Hume’s An Inquiry Concerning Human Understanding, he includes a section on the connection between cause and effect. He draws examples such as one billiard ball moving and striking another, then the second ball moving. Hume goes to some length to convince us that we have absolutely no idea of why one event would cause another. All we have, he says, is a sequence of events that customarily follow each other over repeated experiences.

We only find, that the one does actually, in fact, follow the other. The impulse one billiard-ball is attended with motion in the second. This is the whole that appears to the outward senses. The mind feels no sentiment or inward impression from this succession of objects:  Consequently, there is not, in any single, particular instance of cause and effect, any thing which can suggest the idea of power or necessary connexion. (sic)

Hume mentions many times in this section that we have no idea of how a cause can be connected to an effect. How does heat come about from a flame? How are our limbs moved by our will? When a string vibrates and we hear a sound, we cannot know why we hear a sound, but merely that one customarily follows the other. Indeed, “even in the most familiar events, the energy of the cause is as unintelligible as in the most unusual, and that we only learn by experience the frequent Conjunction of objects, without being ever able to comprehend anything like Connextion between them.”

Hume was very insightful to make this observation. However, he confuses how we learn the connection with whether or not we can investigate it and prove that the cause generates the effect. Yes, we typically learn cause and effect from repeated observation. However, it is not true that the most common effects are as much a mystery as the most unusual and mysterious ones. When we encounter an effect, it may take us a while to learn why the cause generates it. Indeed, in the case of the human mind and will, we may never fully understand all aspects of the cause. But it is not the case that all cause and effect relationships are this way.

In his billiard ball example, we can understand and explain the physics of objects and motion. Newton helped us demonstrate that objects with mass, when in motion, must expend that energy when striking another object. We know why the second ball moves because we know the laws of physics involved in objects in motion. Concluding that the second ball will move is not a case of post hoc ergo propter hoc fallacy.

In Hume’s logic, we would have to lump such things as roosters crowing before the sun rises with billiard balls striking each other. Even if we do not understand a particular cause, it is not the case, as Hume explains, that “We have no idea of the connexion, nor even any distinct notion what it is we desire to know, where we endeavour at a conception of it.”

Sure, Hume is correct that when we see an object for the first time and are ignorant of its properties, we are not able to predict what it will do. And he is also correct that we need repeated observations to first learn the connection between the cause and effect that we observe. But once we do, then we are confident about how billiard balls and violin strings cause things because we know how they work. It is not the case that we forever assume the effect follows the cause merely because one customarily follows the other.

I am reminded of a very old TV show called The Beverly Hillbillies. In the show, a hillbilly family who has never seen modern life is transplanted to a mansion in Beverly Hills. One of the running gags is that when the doorbell rings, the family does not connect the sound of music coming from the walls with the fact that someone pushed the front doorbell button. They merely say that whenever that music comes from the walls, soon after someone always knocks at the door. Hume would have us forever stuck in the Beverly Hillbillies show, never realizing how the doorbell works. However, once we repeatedly observe the effect, we can understand how the mechanism works, and we do indeed know how the cause generates the effect.

About humblesmith

Christian Apologist & Philosopher
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2 Responses to Hume’s Explanation of Cause and Effect

  1. kategladstone says:

    So … Hume says he doesn’t believe in cause-and-effect, and then he says that he doesn’t believe in cause-and-effect beCAUSE …

    In other words, he is saying that his disbelief in causes … has a cause.

    😉 😉 😉

  2. Anthony Parrish says:

    I believe Hume is introducing doubt about verified knowledge. That is, we may be able to understand, through repeated observation, why ball (b) moves when ball (a) hits it but we do not KNOW this. We have developed fine tuned laws of physics that explain how this happens but we have to assume that (1) the laws of physics apply in all cases and (2) the laws a physics apply in the future. In other words we can be relatively confident that all billiard balls we have observed in our lifetimes and in those of previous observers have acted conventionally according to physical laws, but we are making an assumption about billiards in the Andromeda galaxy which we will likely never observe first hand; we are making an even bigger and unfounded assumption about billiard ball behavior in the future. There is no rational reason to assume uniformity of cause and effect; there is nothing about our observation today that mandates uniformity in that same action tomorrow. We assume it will be the same tomorrow for practical, not rational, reasons. A theory such as the Cosmological Principle merely asserts a homogeneous and isotropic universe. We would have to see the entire universe in 3 dimensions plus the entirety of the fourth dimension (time) in order to be sure that there is not a place in the universe where billiards (or anything else) act very different or even opposite of the way they behave here. This assumption is supported by many an observation but not ALL of the possible observations and ALL possible observations are required to be 100% sure. If you were an astronomer and you wanted to tell me that stars obey physics everywhere in the universe, I could ask you how you know star x behaves this way just on the other side of light horizon, in that portion of the universe that is beyond our ability to observe. At best you could say that we have no reason to believe that the laws of physics are different on the other side of the barrier between the observable and un-observable universe, but you could not prove it to me with absolute certainty. Moreover, the astronomer is in the same weak position with regards to events in the future. He or she may have an educated guess that the sun will rise tomorrow but no proof until it does in fact rise tomorrow. We can only be 100% certain about those causes and effects we have directly observed. We are less than 100% certain when we say cause creates effect, both in the past and in the future.

    Naturally it would be very difficult to live a normal life being that unsure of things in the future. In fact it is unlikely an organism could live at all if it internalized this doubt about cause and effect. Thus only those organisms with the gumption to have faith in their grasp on cause and effect survive. This means that we cannot live as human beings without faith in our observations, but it is faith all the same. True knowledge about reality is actually impossible for temporal beings such as ourselves and I think this is one of Hume’s points. No one likes to think about it of course but it is in fact true and is actually one of the few things we know for sure. I think Hume is perfectly aware that human beings can’t really live with this constant doubt but that is a matter of practicality. The matter of fact is: we cannot confirm any facts except those we have already observed.

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