Truth, Theory, Myth?
How do we decide these things,
anyway?
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:
A simple case of falsification
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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.
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.
A more complex process
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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 wellsupported auxilliaries?
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…)
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!
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.
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.
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.
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.
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.
Punc-eek
• Punctuated equilibrium: An overblown
controversy over an answerable question.
• It turns out that evolution varies in tempo.
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 redeployment of a pre-existing collection of parts:
Beautiful, but constrained by history.
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.
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…