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| Roger Penrose |
I thank Plácido Doménech Espí for drawing my attention to this debate held in 2019 between Roger Penrose and William Craig, entitled The Universe: How did it get here & why are we part of it?
Roger Penrose rose to fame as a
cosmologist in 1970 when he proved, with Stephen Hawking, a theorem stating
that the application of Einstein’s theory of General Relativity to the entire
universe requires the existence of at least one singular point in the universe
(a point where all the geodesics of the universe meet). In other words, the Big
Bang.
In 1989, Penrose became one of the most
famous scientific popularizers with The emperor’s
new mind, a book with deep philosophical implications. Among
other things, he proposed the following question, inspired by Gödel’s theorem: how is it possible that we can prove that a theorem is
true, if it cannot be proved mathematically from a reasonable set of axioms?
According to Penrose, this would indicate that human intelligence is
qualitatively different from computing machines.
In 2004 he published a book of extremely
hard popularization, The Road to Reality,
which is full of equations, where he proposes a unification of Einstein’s
general relativity with quantum mechanics (a theory of quantum gravity).
Then came his own cosmological theory, Conformal
cyclical cosmology (CCC), according to which the universe did
not begin with the Big Bang, which would only be the beginning of
the current aeon, but there would be an infinite succession of previous eons,
each beginning with a Big Bang and evolving to global heat death,
when all that would remain in the entire universe would be photons. At that
moment, (no one knows how) the entropy would suddenly drop to a minimum value again,
to start a new cycle.
William Craig has proposed the kalam cosmological argument, which can be
summarized thus:
- Whatever
begins to exist, has a cause of its existence.
- The
universe began to exist.
- Therefore,
the universe has a cause.
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| William Lane Craig |
Craig argues that the Big Bang
was the beginning of the existence of the universe, so there must be a cause
for that existence: an uncaused Creator, existing without beginning, changeless,
immaterial, timeless, spaceless, enormously powerful, and omniscient, to be the
author of the abstract world. In other word: God.
In the debate, Penrose began by arguing
that there are three components of reality: an abstract or Platonic world
(mathematics); a physical world (the material world); and a mental world (the
world of consciousness). In addition, he points out the existence of three
mysteries, which refer to the relationships between these three worlds:
- The unreasonable effectiveness of mathematics (Eugene
Paul Wigner): Why does the abstract world describe so well the workings
of the physical world?
- The origin of consciousness: How can consciousness
arise from the physical world?
- The mind’s ability to understand the abstract world:
Why can we understand mathematics and apply it to describe counterintuitive
phenomena?
Craig agreed with Penrose’s analysis, and added
this consideration:
The abstract world cannot be the cause of the other two worlds,
the physical and the mental, because it has no causal power and cannot make
decisions. It is not clear that the physical world is the cause of the mental
world: Penrose himself admits that this is a mystery. Can the mental world be
the cause of the physical and the abstract worlds? It appears it can: we have
the experience that our minds can produce physical changes through human
intentionality. Could there not be an omniscient mind who is the author of the
physical and the abstract worlds? That would solve the problem of the origin of
the three worlds.
To this, Penrose could only reply that he
does not like this idea (he declares himself an atheist) and would rather think
that the abstract world is primordial, although he does not know how the other
two worlds could proceed from the abstract world.
The second part of the discussion dealt
with the fine-tuning problem.
Craig indicated that there are three solutions to the problem:
- Universal constants must have the value they have.
- Our
existence in such a fine-tuned universe may be due to chance in a multiverse.
- Our universe has been designed by a Creator.
Penrose began by denying that fine-tuning is
a fact, although he ultimately declared himself agnostic about this question.
He proposed his CCC theory as an explanation of the origin of our universe.
Craig pointed out that this theory is just another multiverse theory, in time rather than in space,
(most multiverses are supposed to exist in space). Penrose, for whom this idea seemed
to be new, embraced it happily and asserted that his theory has been experimentally
confirmed, an assertion most current cosmologists would not accept.
My conclusion from this debate: Penrose
was mostly on the defensive, and he was unable to offer one convincing argument
in favor of his atheism.
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