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Lecture 8

PHLA10H3 Lecture 8: Evolutionism and Creationism

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William Seager

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September 29, 2015
PHILO Lec 08
Casket Problems:
The prize is in the silver casket: The gold statement is false, the bronze one tells the truth, the
silver statement , the second is Gold
Abduction and Alternatives
Recall: the strength of an abductive argument depends on the explanatory power of the
hypothesis compared to its rivals, plus the overall plausibility of the hypothesis.
Example: AIDS testing
oSuppose someone (P), with absolutely zero known risk factors tests positively for
AIDS. Suppose the test is 99% reliable (chances are 99% that if you have AIDS
you test positive)
oTwo hypotheses
H1: P has AIDS
H2: P suffered a “false positive
oWhich hypotheses should be favoured?
oThis depends on two things:
oHow plausible is it that P has AIDS independently of the test result
oWhat is the false positive rate?
Let’s say the FP rate is 1 in 1000 and the background rate of AIDS in the
population is 1 in 100,000
oSo what is the chance that P has AIDS? About 1 in 100!
oThis is the Base Rate Fallacy
The hypotheses (H1) of design beats the hypothesis (H2) of random creation of
How much independent plausibility does it have?
Are there any alternatives to design which do better than the random creation hypothesis?
There is H3: organisms evolved by natural selection
Evolution and Creation
There are two hypotheses to the theory of evolution that Darwin developed: the Tree of
Life and modification by natural selection
A single tree of life
One tree of life means all living creatures are
descended from one “original organism”
Modification by natural selection
Modification by natural selection involves
some extra hypotheses:
Offspring inherit the characteristics of their
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There is slight variation in inheritance
Some variations increase the fitness of offspring
Example of artificial selection: the bulldog, collie and dachshund all descended from the
wolf. There is a lot of variation in breeds of dogs that evolved from generation to
A special case: Speciation
Evolution works by very gradual modification.
How can new species arise
There is a single population of zebras. A small number of zebras have been somehow
separated from the rest of the population, splitting the population in two. If the resulting
populations live in different environments, selection will lead them to become
increasingly different
Darwin at the Galapagos Islands: birds developing variation in beaks to better equip
themselves to hunt and survive
Evolution and Creationism
There are three different approaches to the problem of evolution
Theistic evolutionism
oGod created the world, set mindless evolutionary processes in motion and then
stepped away
oLet evolution take its course from there
Atheistic evolutionism
oThere is no God or superior being that created the mindless evolutionary process
oThere are only physical processes leading to evolution that are responsible for
complex adaptations we observe organisms to have
oGod created the world
oGod directly intervenes in nature to maintain the mindless evolutionary processes
in motion
oYoung earth: the Earth is only around 4000 years old
oNo speciation: there can be evolution within the species, but you can’t create a
new one that doesn’t descend from a previous species
Weak Creationism Arguments
Creationists argue that evolution is “only a theory and we are not certain of this theory
because hypotheses about the distant past can’t be proven with absolute certainty; we
don’t have sufficient evidence
oThis is true of all science. Nothing in science is absolutely certain. However,
what a scientist legitimately strives for is evidence powerful enough to prove that
an explanation is a lot more plausible than the competing explanations. This
evidence does not have to be directly observable. Ex. Evidence about the
evolution of the homosapien species millenniums ago
oThe question is: what kind of evidence can you accumulate from the theory?
Thermodynamics makes evolution impossible
oThe theory of how complicated systems develop over time
o2nd law theory: No order from disorder by natural processes
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