Truth, Theory, Myth?

1. Truth, Theory, Myth? How do we decide these things, anyway?

2. Testing • In most cases where we talk about truth, there are pretty straightforward methods that (at least in principle) can be applied to determine what is or isn’t true. • Claims that don’t directly report observations have consequences for our observations all the same. • So here’s a picture of how we might go about putting a claim to the test:

3. A simple case of falsification • T • If T, then O. • But we observe not O. • Therefore not T. • But does this ever fit what happens in science? Consider the theory of gravity: No particular (observable) motion of any object is implied just by the theory.

4. Auxilliaries • To derive any claim about observable motions using Newton’s theory, we need other claims about the situation (claims that can in turn be tested by observation, at least indirectly). • To show that planetary orbits will be ellipses with the sun at one focus, Newton assumed the mass of the sun was much larger than that of the planets, and that the gravitational influence of the sun is enough to calculate, within acceptable limits, the planets’ trajectories. • So he came up with a simple model in which the objects standing in for the planets obey the rules of his physics and travel in ellipses around the object standing in for the sun.

5. A more complex process • T & Aux • If T & Aux, then O • Not O • Therefore, not T or not Aux • Here falsification is never fully conclusive, but it does add up over time– how seriously could we take a theory that never seemed to get predictions right when we combined it with well-supported auxilliaries?

6. But this is so negative • Testing involves looking for evidence that a theory is false. But if we’re worried about truth, that’s not enough. • How can we go about actually finding evidence supporting a theory? What’s involved in having a well-supported theory? • One answer is that it must pass detailed, careful tests. • Success at these doesn’t show the theory is true, in general (Newton was wrong about gravity, after all…)

7. Constraints • However, as a theory passes these tests, we acquire more detailed and general knowledge about the phenomena the theory is about. • Any theory of those phenomena will have to pass these same tests– so these constraints mean that any acceptable theory has to capture all (or at least a very large amount of) the successes of its predecessors. • So, for instance, could we find out, in the future, that all this evolution stuff (i.e. common descent) has been a mistake? • In principle yes– but it’s a very strange sort of story!

8. Two extremes • Haeckel as the extreme supporter, who simply posits whatever his evolutionary ideas require. • Agassiz as the extreme skeptic, who rejects evolution but has nothing but ‘poof’ to offer in its stead. • Science aims both to test its theories, and to accept (pro tem) theories that have passed (and continue to pass) detailed testing against the evidence. Neither Haeckel nor Agassiz’s stance allows this.

9. The middle ground • Darwin recognized that more evidence was worth looking for, even where he had a good response to the objections for now (transitional fossils, intermediate forms of wings and other organs). • More evidence has since been found, on these and many other fronts. • In this sense, evolution is an immensely successful theory, but the story is not (and never will be) complete: there are more tests to come, though scientists become quite confident as more and more tests, covering more and more types of evidence and process, continue to support evolution.

10. Induction • The problem of induction arises here: how do we justify conclusions that reach beyond the evidence (strictly and narrowly construed)? • Some choose to be skeptics about this– but they are clearly insincere (or, at least, unable to resist acting on induction even though they question it). • A better route: Science distinguishes reliably established phenomena (details of various fossils, anatomical and physiological facts about organism, planetary motions across the night sky, atomic spectra, genetic similarities between various organisms, etc.) that we can produce/ observe regularly and establish patterns in) from theories that explain these phenomena and reach far beyond them.

11. Phenomena and theory • A theory reaches out, it has implications about phenomena that we haven’t yet observed. • Even when it fits the phenomena we have observed, it just might fail when tested against new ones. • In physics, new energy levels/ length scales, etc. reveal (sometimes) phenomena that our older theories can’t capture. • But the phenomena they did capture are still there, including the patterns our old theories predicted and explained. • So any new theory has to be pretty conservative when it comes to older, well-established phenomena.

12. Evolution again • So the trees of taxonomy, development, the fossil record, biogeography, and biochemistry are phenomena—and their shared structure is too. • Common descent is the only credible account of these. • And the mathematics of population statistics and genetics show that natural selection is the principle force behind evolutionary change over time. • Evolution in both senses is so well-founded, we need to invent a kind of conspiracy theory (recall Gosse) to imagine a situation where it could turn out to be refuted by future evidence. • Still, as always, there is more work to be done, more details to discover, more hypotheses to test.

13. Punc-eek • Punctuated equilibrium: An overblown controversy over an answerable question. • It turns out that evolution varies in tempo.

14. Three views of life • God as clockwork designer. • ‘Programmed evolution’ (evolution with teleology). • ‘Contingent evolution’ (evolution as a comprehensible causal process with no discernable ‘final cause’). • The fertilization of orchids: creative shift and re-deployment of a pre-existing collection of parts: Beautiful, but constrained by history.

15. From Science to Philosophy • Does evolution teach us anything about ourselves, about the meaning of life, about …? • Does it, in particular, imply that life is meaningless, purposeless, etc.? • Are we destined to ‘increasing marginality in an uncaring universe’? • Young urges ‘caution and moderation’ here, with respect to how we apply our evolutionary science to philosophy and religion.

16. Disciplines and authority • In fact, Gould himself advocated a line separating religion and science. • Separate but equal, non-overlapping ‘magisteria’ (= areas of teaching). • I’m not convinced that this is the right response. Authority has to be earned, and while science succeeds in producing agreement by persuasion, religion (at least doctrinal religion) is a failure in that respect. • The freedom to believe we call freedom of conscience is a fundamental right. • But it’s held equally by all, and must not be handed over to self-proclaimed doctrinal authorities…