Wednesday, 2 April 2014

Negative Causation: a brief refutation

For a handful of philosophers the notion of absence gives rise to concerns over the nature of causation. Jonathan Schaffer of Rutgers University, for instance, argues that 'negative causation', as he calls it, is a 'genuine form of causation' in which 'causes need not be physically connected to their effects.'

At first blush, the concept of negative causation seems to fit the facts quite well. Pull a ladder from under someone and the absence of support precipitates a fall. Sever someone's wages and the absence of income will likely cause significant disruption. What is blindness other than an absence of vision, or ignorance other than an absence of knowledge?

Whenever we discuss causation we tend to talk in terms of influence and the exchange of forces. There is nothing contentious about this. Schaffer provides a long list of instances where the removal of some impediment triggers a consequence or chain of events and he argues that in each case we have indisputable evidence of causation through absence. He gathers together many plausible examples from a broad range of fields, yet one crucial point goes unmentioned. If causation arises in a negative form then it should, like its positive sibling, come in varying degrees or states. Photographic negatives consist of tonal gradations from transparent to opaque; negative numbers mirror their positive counterparts and even the theory of negative energy is not limited to a single state.

Another helpful way to appreciate the conceptual error is to recast negative causation as zero causation. Interestingly, as soon as we do so, it becomes obvious just where the fault lies: zero causation is zero influence. 

We don't need a theory of negative causation. Absence works perfectly well to designate the lack of causal influence. And the only reason we might be tempted to say that absence exerts influence is because, in the absence of influence, other forces come into play that would otherwise be held in check.


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