# the tipping point

Some would say that the “tipping point” phenomenon is an example of “vertical causation”.

This is where a pile of sand has built up gradually, as grains trickle onto it from above. The effect can be seen in an hourglass. Apparently, the slope of such a sandpile will never exceed 43.5° (though I guess the exact angle will vary with the type of sand). When that point (the “tipping point”) has been reached, just one more grain falling onto the slope will cause a “landslide”, the base area of the pile will increase, and the slope will stabilise again at or below 43.5°.

The tipping point phenomenon is a very good example of how a tiny immediate cause can have a relatively massive effect. Of course, the bigger picture includes not just the last grain to fall before the landslide, but all the grains that fell before that and brought the pile to the delicate condition in which just one more grain was required to set it off.

Anyway, this is not an example of vertical causation. The tipping point is certainly a higher level phenomenon than any of those that might be demonstrated by an individual grain, but it, in itself, exerts no effect on the grains. The movements and eventual disposition of each grain are affected only by those of the other grains with which it comes into contact (as well as gravity etc.). When we measure the slope at the tipping point as 43.5°, the consistent precision of that figure might tempt us to think of it as specially significant—and in a sense it is: it's quite fascinating that the features of the individual grains, when aggregated, come to this. But it is not causally effective. What are, are the relationships between all the grains that come into contact. Which is why, as I say, the tipping point will vary with the features of the individual grains, the type of sand. It is just an overview, a simplification, of all the relationships between all the individual grains in the pile. The tipping point phenomenon cannot affect the behaviour of individual grains precisely because it is that behaviour, in aggregate.

Despite the impression that might have been given above, I am not a reductionist, and here is why: I would insist that the tipping point phenomenon is just as real as are the features of the individual grains. Molecules are as real as atoms, and higher level phenomena generally are just as real as lower level ones. But I also insist that “levels of explanation” are well-named: that causal explanations have to adhere to one level to be coherent.

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