Comparing apples and oranges


We’re not supposed to compare apples and oranges – or so the saying goes. But as H.P. Glenn, erudite author of Legal Traditions of the World points out, we can compare apples and oranges: “[t]here are obvious criteria of roundness, acidity, colour, sweetness, price and so on. “ As Glenn goes on to ask, “Why do people say you cannot compare things, that they are incommensurable, when they are so obviously comparable or commensurable?”

A bit of etymology may be in order: ‘incommensurable’ is the negation of the Latin ‘com’ and ‘mensurabilis,’ indicating, as Glenn says, “a degree of common measure.” Incommensurable, in other words, is a fancy way of saying that things are incomparable. The term derives from debates in ancient Greek mathematics: there was an issue at the time of whether everything mathematical could be expressed in integers, and the Pythagoreans demonstrated that some aspects of geometry could not be so expressed.

I mention all this not out of sheer pedantic interest, but because some friends have been urging the notion of incommensurability on me recently in the context of energy policy debates. Oddly enough, the abstruse idea of incommensurability has implications for our energy choices. Consider, my friends say, the diverse social, economic and environmental goods at stake when we need to make decisions about electricity generation – these goods cannot be compared to each other, their argument goes, against a common measure or standard. A coal plant, say, provides reliability and security for hospitals and homes, it drives economic growth in a region, and yet it generates carbon emissions. Hospital reliability, economic growth, the greenhouse gas buffering capacity of the atmosphere – these are three quite different goods from each other. These goods cannot be assigned quantitative values in such a way that the greatest numerical value will simply trump the others tout court.  

Fair enough. I acknowledge there is an intellectual challenge when we attempt to compare social, economic and environmental goods in connection with coal plants, and I agree that a simplistic quantitative standard will not do justice to the complexity of the reflection. The incommensurability literature – recalling its roots in ancient Greek philosophy – rightly cautions us against reductionist mathematical approaches. We won’t find a magical formula for weighing various goods against each other.

Even so, I want to resist jumping from this caution to a conclusion that we cannot meaningfully bring diverse goods into comparative relief. Whether the term ‘incommensurable’ is used descriptively (we cannot compare these goods) or normatively (it would not be fair to compare these goods), my instincts tell me that we need to be careful in invoking it: some comparisons may be difficult or unlikely, but precisely for this reason they also may be all the more worthwhile or revealing to us. I worry, moreover, that talk of incommensurability encourages a kind of intellectual paralysis in the face of competing goods. As Glenn points out, “If two things, or societies, or scientific paradigms, are incommensurable, then you cannot conclude anything about their respective merits. They simply are.” Continuing with our coal plant example, it has become a conversational commonplace that China is constructing the equivalent of two 500 MW coal plants per week (or some variation on this number). But surely we we can do more than simply observe, as a problem for thought, that various goods are at stake when China builds so many coal plants. Surely we can and must think our way through this problem. As a consultant friend of mine likes to say, “Academics like to ‘problematize.’ And ‘problematizing’ is easier than solving problems.”

In the movie An Inconvenient Truth, Al Gore reproduces an image of a weight scale with some bars of gold on one scale, and planet earth on the other scale. As I recall, the image had been used in an industry presentation somewhere to represent the difficulty of making choices between economic and environmental goods before Gore got his hands on it. Says Gore of the comparison mockingly, pretending to weigh his hands in the air as though stumped by the choice, “Hmm … some bars of gold, or the entire planet … bars of gold or the entire planet …” The audience laughs approvingly. An advocate of the idea of incommensurability might be tempted to invoke Gore’s example to illustrate how these two goods cannot meaningfully be compared to each other. I draw the opposite conclusion: Gore’s mockery forces the listener to engage the comparison on its face – between a few bars of gold and the health of the entire planet. The laughter of the audience indicates that these things can be compared, and that one can draw a conclusion (and easily, in this case) as to their respective importance.

Comparison among different types of goods may call for novel forms of reflection. It may even require us to generate new categories of thought and judgement (so for instance in the context of energy policy, even as they speak of incommensurability, my friends seem prepared to allow that sustainable development theory may have something to say at a meta-level about the relative priority of diverse forms of goods). Any categories we may invoke will have their limits, and academics will problematize them as such. But let’s not be too quick simply to dismiss altogether comparisons among putatively incommensurable goods. Policy makers facing difficult choices would likely benefit from our undertaking such comparisons, however unlikely or odd they may seem to us a priori.


One thought on “Comparing apples and oranges

  1. Interesting post John. That scene from An Inconvenient Truth also came to my mind as I was reading it.

    However, I do not understand how incommensurability is involved in the coal plant example. You mention two good things it provides, energy and economic growth, and one bad thing, carbon emissions. It seems obvious (to me at least) how we might go about ranking different combinations of these goods.

    Best of all would be some type of energy plant that provided energy and economic growth and zero carbon emissions.

    Second best would be an operation like the coal plant: energy and growth along with emissions.

    Worst of all would be an institution that resulted in carbon emissions, but did not provide energy or economic growth.

    The problem in this area would seem to be designing energy technology that reflects our judgement about what type of arrangement is best, not an inabilty to make such a judgement in the first place.

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