Not everyone thinks we need causation in science. Causation is so hard to pin down and so easy to get wrong, so why don’t we instead just stick to the data? Without speculating over causal relationships we could then establish that people are happier without children, that married men live longer and that life expectancy for smokers is ten years shorter than for non-smokers. What more do we need to know?
The question is what we can do with this information. Could it guide our personal decisions at all? If I want to be happy, should I choose not to have children, for instance? And if a guy wants to live longer, should he get married? If so, we seem to think that these results have validity beyond the data-set from which they are derived, and that we can use such data to predict how people will behave elsewhere at other times. But what’s the justification for this?
Let’s say we have based our information about life expectancy of married men on statistical data from a sample of 100.000 men. Surely this says something about married men in this particular group. But unless we can offer an explanation – a causal one, that is – of why there is such a correlation, there’s no reason for us to conclude that marriage somehow affects life-expectancy in men.
If science is supposed to offer theories, explanations and predictions, causation is essential. This doesn’t mean that we don’t need correlation data. They can be very good indications of where to search for causation. But they are not themselves sufficient to guide our individual decisions. For this we need to understand the causal processes involved.
This article from Harvard Medical School, for instance, offers a number of causal explanations of why married men live longer: stress, diet, life-style, loneliness, depression. Once we have placed causation correctly, we can see why the marital contract as such isn’t the real cause of prolonged life-expectancy in men. Surely some marriages are the direct cause of all of these life-threatening factors. So rather than getting married to live longer, one might think of eating healthy, de-stress, and work on one’s social network and personal relationships – if this is where the real causal work is done.