Hume rejects causation on essentially empirical grounds. We cannot perceive a mechanism for causation, and so we cannot know that it exists. I agree that causation does not exist, but I disagree that radical skepticism can be inferred from this view.
Firstly, the word causation is an abstraction from “cause and effectâ€, which may be understood as two events. By definition, of course, any cause implies an effect, so there is no grammatical or logical objection to the word “causationâ€. In fact, causation is a logical term – it belongs to the realm of logic – and therefore has as its subject matter language itself, and not the events witnessed.
Every word has a definition. Only nouns name something that actually exists. When we say “I am walkingâ€, we don’t mean that we are walking itself, nor do we mean that walking has size or shape. Despite twentieth-century attempts to proclaim “isness†as something, it is not anything. So let’s take the noun “billiard ball†as an example. Don’t know why – it just popped into my head. In any event, what I have to say here will apply only to nouns, if for no other reason than simplicity.
Every definition “delimits†that which is defined – this much is evident in the etymology of the word “definitionâ€. In common parlance, we delimit the meaning of any word only enough to make that word useful. The philosopher, like the scientist, must often go a bit further, and hone meanings, and therefore definitions, a bit further. We can accomplish this by describing various additional properties of an object – properties that we don’t ordinarily include in a definition. To say that a cat is a quadruped is to give part of the definition, but not enough even for most common usage. But whatever we need to add to this definition to make it useful in ordinary speech, we can add. We can add more properties – and by properties I mean just this – additional description – beyond what we need in a dictionary entry.
For instance, we would not ordinarily see the boiling point of water listed in a dictionary – because most usage of this word would not require that we know the boiling point of water. But the scientist might need to know this, and anyone might, for certain purposes. So, the boiling point of water is an additional (to the dictionary entry, to what we usually would call the definition) property of water – a description beyond what we normally take for a mere definition. This is not to say that the dictionary entry doesn’t include properties – it will usually not include all of them that we know.
So, what causes water to boil? What causes a billiard ball to move when struck by another ball? Well, a billiard ball is spherical, made of plastic and colored one of several standard ways. While there are a couple of different sizes these balls are found in, there is a standard size. A billiard ball six feet across would surely be called a “giant†billiard ball. No matter how persnickety we may wish to be, we can, with some effort, agree on what a billiard ball is. Oh – and a further property of billiard balls is that they move when struck by another ball (with force sufficient to overcome the friction of the felt), or by a cue stick, or by a shoe. In other words, the “cause and effect†relationship between billiard balls is part of the (extended) definition of “billiard ballâ€, just as the boiling point (or points, as this is affected by altitude or atmospheric pressure) of water is part of the (extended) definition of water.
Object A does this when that happens. Or, A = (definition), but sometimes A = (definition plus description, or additional properties – depending on the need at hand). I am only trying here to acknowledge that dictionary definitions don’t always tell the whole story.
A billiard ball is a billiard ball if and only if it will move when struck by another object, or the table is tilted, or…………fill in the cause of your choice.
But this cause is only another description, or extended definition of the object that strikes the ball we are observing as an effect. The only complication is this – the “cause†is something that is changing if only position. We will need a description of a particular ball (for instance) at a particular time – we are looking for a property of that particular ball at that time – that it is in motion. And the “effect†is not the second ball in any state we may find it, but the ball in motion.
This is, of course, exactly the phenomenon that Hume was observing. There is, indeed, no mechanism for causation – except language itself. Our description itself is the mechanism – and this is language, which does not exist in space/time. Causation is a brain function because language is.
Radical skepticism looks for substance where it does not exist, and then proclaims that it does not exist. But billiard balls do exist.
Causation requires definitions not just of objects, but of objects changing somehow. “Causes†are objects as they change (position, for instance) and so are “effectsâ€. This may be a chemical change, of course, as is the case with water. But Hume treated billiard balls as static objects, and so thought that an additional something, causation, was required to explain their motion. Or so he said. It just isn’t. All that is required is to note that any causation is a description of a particular – an object as it changes (again, if only position).
I may be said that I am merely describing “virtuesâ€. But I do not mean to say that these properties “belong†to the objects so defined, but that they are part of our description of those objects. They belong to language. Causation is an analytical term, because it is an abstraction from language itself – from a previous abstraction. “Ball†is an abstraction from an observed phenomenon – part of a Russellian “object languageâ€. Causation is a second-order abstraction, none of which exist.