6.1 The Meanings of Cause

Before we proceed, we must issue something of a disclaimer: when we say that one action or event causes another, we don’t really know what the heck we’re talking about! OK, maybe that’s putting it a bit too strongly. The point is this: the meaning of ‘cause’ has been the subject of intense philosophical debate since ancient times (in both Greece and India)—a debate that continues to this day. Myriad philosophical theories have been put forth over the millennia about the nature of causation, and there is no general agreement about just what it is (or whether causes are even real!)

We’re not going to wade into those philosophical waters; they’re too deep. Instead, we’ll merely dip our toes in, by making a preliminary observation about the word ‘cause’ to provide some hint as to why it’s been the subject of so much philosophical deliberation for so long. The observation is this: there are a number of distinct, but perfectly acceptable ways that we use the word ‘cause’ in everyday language. We attach different incompatible meanings to the term in different contexts.

Consider this scenario: You’re in your backyard vegetable garden with a small child, a 4-year-old family member perhaps. The child, who is ‘helping’ by watering some of the plants asks, Why do we have to water the plants? You might reply, We do that because water causes the plants to grow. This is a perfectly ordinary claim about cause and effect; it is uncontroversial and true. What do I mean by ‘causes’ in this sentence? I mean that water is a necessary condition for the plants to grow. Without water, there will be no growth. It is not a sufficient condition for plant growth, though: you also need sunlight, good soil, and so forth.

Consider another completely ordinary, uncontroversial truth about causation: decapitation causes death. What do I mean by ‘causes’ in this sentence? I mean that decapitation is a sufficient condition for death. If death is the result you’re after, decapitation will do the trick on its own; nothing else is needed. It is not (thank goodness) a necessary condition for death, however. There are lots of other ways to die besides beheading.

Finally, consider this true claim: smoking causes cancer. What do I mean by ‘causes’ in this sentence? Well, I don’t mean that smoking is a sufficient condition for cancer. Lots of people smoke all their lives but are lucky enough not to get cancer. Moreover, I don’t mean that smoking is a necessary condition for cancer. Lots of people get cancer—even lung cancer—despite having never smoked. Rather, what I mean is that smoking tends to produce cancer, that it increases the probability that one will get cancer.

So, we have three totally ordinary uses of the word ‘cause’, with three completely different meanings:

• cause as a necessary condition
• cause as a sufficient condition
• cause as a mere tendency (neither necessary nor sufficient)

These are incompatible with each other, but each is acceptable in its context. We could go on to list even more uses for the term, but the point has been made. Causation is a slippery concept, which is why philosophers have been struggling for so long to capture its precise meaning. In what follows, we will set aside these concerns and speak about cause and effect without hedging or disclaimers, but it’s useful to keep in mind that doing so papers over some deep and difficult philosophical problems.