Rings and Bridges

Yesterday’s post was about “ring species”, both as interesting natural phenomena in themselves, and as a reminder that the persistent human tendency to impose discrete categories on continuous phenomena can lead us, if not to outright error, at least to an inaccurate model of the world. Keeping in mind that we are all inclined toward this prejudice — Richard Dawkins calls it the “tyranny of the discontinuous mind” — can help us to avoid not only taxonomic pitfalls, but philosophical ones as well.

There are, of course, occasions when we must impose abitrary boundaries on continuously varying properties. A good example is the voting age. There are obviously serious and thoughtful seventeen-year-olds whose political savvy and judgment far exceeds that of many of their elders, but, since a qualification test for eligibility to vote is a bad idea for a number of good reasons, we need some consistent way of deciding who gets to vote and who doesn’t, and so we draw a line according to age. We try to place the line in a fair place, and although we know that we temporarily exclude some teenagers who would be responsible voters, we aren’t too troubled about that, because we know they’ll get their chance soon enough.

But some of of the thornier issues we must resolve don’t lend themselves so well to arbitrary line-drawing, because there are more serious moral consequences to where we draw our boundaries. Perhaps the most troublesome example is the gradual transition of a just-fertilized ovum — a single cell — to a full-term fetus. The question of animal rights also turns on similar issues: we tend to be protective of what we consider the “higher” animals — chimps, dogs, dolphins, and so forth — because we believe that their subjective awareness, their ability to experience the harm we might cause them, is sufficiently advanced to warrant their inclusion in the “charmed circle” of moral consideration. We are rather less solicitious of, say, chickens — we would rather that they are treated well, but most of us don’t mind slaughtering and eating them (or at least having others do it for us) — and I think there are very few of us who worry much about the suffering of mosquitoes, or bacteria. At what point along the continuum of complexity should we consider an organism to have acquired subjective consciousness?

This all bears directly on the rancorous philosophical debate regarding “original” versus “derived” intentionality, which turns on the apparent discontinuity between the “aboutness” of human minds and the inertness of inanimate matter. Some philosophers have flatly declared this to be an unbridgeable gap, but as I have argued here and elsewhere, I think there is no reason why meaning and intentionality cannot have entered the world gradually, as more complex organisms, with more complex interests and behaviors, came into being. Daniel Dennett has compared these sorts of discontinuity arguments to the notion of the Prime Mammal, an argument that goes like this (taken from Freedom Evolves, p.126):

  1. Every mammal has a mammal for a mother.
  2. If there have been any mammals at all, there have been only a finite number of mammals.
  3. But if there has been even one mammal, then by (1), there must have been an infinity of mammals, which contradicts (2), so there can’t have been any mammals.

This is obviously absurd, and at the heart of the fallacy is our natural tendency to impose the dichotomous “mammal”/”non-mammal” distinction on a connected lineage of creatures that, if we look far enough back, are clearly not mammals, and which, much more recently, clearly are. Presumably, between the two extremes were a series of what Dennett calls “hard-to-classify intermediates”. Mammals breed only with other mammals; should we assume that there was at some point a mother that would have been physiologically unable to mate with her offspring? Almost certainly not, but somehow we made the transition from reptiles to mammals without any need for an abrupt discontinuity. And I agree with Dennett and others that to insist that there is such a boundary in the history of intentionality is to commit the same errror.

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