Whales, fish, and analytic propositions

What is a child learning when he learns that a whale is not a fish?

You are on a whale-watching trip, accompanied by an eight-year-old and a philosopher. Your party is in luck: not a hundred yards from your vessel, a blue whale comes to the surface, blows, and goes back under water. The eight-year-old says, “Wow! That’s the biggest fish I’ve ever seen.”

You’re not so clueless as to spoil the child’s joy with a taxonomy lesson, but sometime later in the day you explain that a whale, though it lives in the water, is not a fish, but a mammal: a fish is cold-blooded, lays eggs, has scales, and uses gills to “breathe” water, while a whale is warm-blooded, bears live young, has skin and hair, and emerges to breathe air through lungs.

Later, at dinner, you and the philosopher discuss the nature of the propositions involved. Is “A blue whale is not a fish” analytic or synthetic? That is, is the proposition clearly true once you know what a blue whale is and what a fish is, like “This square has four equal sides” or does it contain new information, like “This square has area 10”? And is it a priori (knowable in advance without any investigation) or a posteriori (requiring empirical verification)? And are those two sets of categories co-extensive, or are there propositions that are both synthetic and a priori?

Hilzoy’s story about a dream in which she was a synthetic a priori proposition trapped in a crowd of hostile philosophers reminded me of the question, and of the whale-watching example that came to mind as I was listening to a paper on the topic as part of the excellent seminar series maintained by the UCLA philosophy department.

To my mind, the example shows that neither the analytic/synthetic distinction nor the a priori/a posteriori distinction can be made of propositions in the abstract; both depend on the prior state of knowledge of the person encountering those propositions.

I claim that in some important sense the child knows perfectly well what a blue whale is: he can (let’s suppose) reliably distinguish blue whales from things that aren’t blue whales when presented with photographs. So “knowing what a blue whale is” doesn’t by itself include “knowing that a blue whale is not a fish.” For that, the child would need to know facts about whales (e.g., that they are air-breathers) and “facts” about taxonomy (that biologists define “fish” in terms of physiology and not merely habitat). In a culture that defined fish in the same naive way the child does, as “something that lives in the water,” his claim that a blue whale is the biggest fish would be correct.

So it seems that, for the child, “a blue whale is not a fish” is a synthetic proposition, conveying new information. But once he’s learned that new information, “That blue whale you’re looking at right now is not a fish” is a priori; once he knows that the being in question is a blue whale, he doesn’t have to watch it blow to make sure it’s not a fish. Have we found a proposition that is both synthetic and a priori?

Now consider instead a college student taking her first taxonomy course. She starts out by knowing that fish are cold-blooded. Given that background knowledge, when she learns that whales are cetacea, an order of the class mammalia, and learns what the characteristics of mammals are, including warm-bloodedness, she knows, without being told anything more, that whales aren’t fish. For her, it is now analytic that no whale can be a fish, and a priori that any particular whale is not a fish.

So, I claim, “A blue whale is not a fish” or “That specific blue whale is not a fish” can be analytic when presented against one set of background knowledge, but synthetic when presented against another set of background knowledge. That leaves unresolved the question whether the same proposition could be both synthetic and a priori to the same person at the same time, so it may not be sufficient to rescue Hilzoy from her nightmare.

Now, I would estimate the probability that this line of thinking and cogent criticisms of it are both well-known to analytic philosophers at no less than 95%. (Could this be the basis on which Quine criticized the analytic/synthetic distinction?) I’d be grateful to any reader who can point me to the relevant literature.

Author: Mark Kleiman

Professor of Public Policy at the NYU Marron Institute for Urban Management and editor of the Journal of Drug Policy Analysis. Teaches about the methods of policy analysis about drug abuse control and crime control policy, working out the implications of two principles: that swift and certain sanctions don't have to be severe to be effective, and that well-designed threats usually don't have to be carried out. Books: Drugs and Drug Policy: What Everyone Needs to Know (with Jonathan Caulkins and Angela Hawken) When Brute Force Fails: How to Have Less Crime and Less Punishment (Princeton, 2009; named one of the "books of the year" by The Economist Against Excess: Drug Policy for Results (Basic, 1993) Marijuana: Costs of Abuse, Costs of Control (Greenwood, 1989) UCLA Homepage Curriculum Vitae Contact: Markarkleiman-at-gmail.com