So what is the "Argument from Reason" (AfR)?
In short, it's a way to crash together two compelling
yet conflicting world-views.
The first is naturalism -- the view that the universe is
a deterministic, physical process
in which the movements of mindless atoms are dictated by
the laws of nature.
The second is reason, a process in which thinking humans
derive propositions from other propositions
based on the laws of logic.

Suppose, for example, that a mathematician is thinking rationally,
and developing the logical consequences of a set of axioms.
From a naturalistic perspective, nothing is happening here except
a bunch of totally automatic chemical reactions
in the man's head.
Those chemical reactions (as chemical reactions) can't perceive
propositions or the laws of logic.

They follow their own necessity.
This raises a doubt about whether the man's conclusions are being
determined by their content
(i.e., the ideal mathematical objects he is thinking about)
or by the chemical processes in his brain.

If we take naturalism seriously, it seems the chemical processes
must be in the driver's seat.
But that casts reason itself into doubt --
a major problem for a reason/science-based doctrine like naturalism.

That's the AfR in a nutshell,
and Reppert presents a number of variations on this basic theme.

But wait, you say: What about computers?
Surely they show that naturalism and logic are compatible.
After all, if a computer (a mindless physical process), can implement
the laws of logic,
then doesn't that prove that physical things can be sensitive to
logical laws?

That's an excellent point, and it occurs to almost everybody
who encounters the AfR.
Indeed computers are at the very heart of the problem posed by the AfR.
But simply pointing to the computer as a refutation to the AfR
(as tempting as that is!) doesn't really work
and that's another charm of this book: the deceptive depth of the AfR.

To illustrate, consider a couple of critics of Reppert.
Steven Carr, a computer programmer, writes:
"The point is that a purely material thing can manipulate
very abstract non-material things
(software classes, pointers, variables etc)."

What an astounding statement!
It harks back to Descartes' substance dualism, and the intractable
problem that stumps everybody:
how can material bodies and immaterial souls interact?

In critiquing the AfR, Carr has essentially yielded to it,
allowing that there is a quasi-Cartesian dualism between the material
(hardware) and non-material (software).
A view like that is actually very congenial to a Christian --
or, more generally, an anti-materialist -- worldview,
and is exactly where C. S. Lewis and Reppert want to take you
with the AfR.

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“If a materialist says that she believes in materialism
because she perceives the reasons for believing it,
then I take it she is committed to the existence
of reasons,”
and therefore has to explain how they can exist in a
materialist universe.
It is really the same argument that Socrates used at his
defense: How can you believe in flute playing and not
believe in flutes? How can you believe in divine effects
and not believe in the gods?

Reppert has updated it and applied it to the existence of
reasons in a useful and persuasive manner.
His refutation on pp. 100-101 of the notion that reason
could have been produced by natural selection
is also good.

The “inadequacy objection,” which argues that non-scientific
explanations do not explain, is one of the biggest hurdles
the argument from reason has to face.
Reppert’s question on p. 111 is an excellent response to it:

“Is it more dangerous to the scientific enterprise to suggest
that a comprehensive “scientific” account of cognition
cannot be correct,
or to suggest that truth should not be the goal of our
rational deliberations?”

That is a question that we need ask more insistently.

..I focused on the fact that a naturalist universe is by
definition a deterministic universe. The laws of physics
determine everything because the universe, being uncaused,
exists a se and therefore by definition cannot be other
than it is.

It seems to me that this fact needs to be stressed,
for it provides a simpler way of defeating Anscombe's
objections.
It really does not matter whether chains of reasoning
caused by non-rational causes can happen to have been
valid or not,
unless we are free to choose between them on a non-deterministic basis:

If nobody can help believing what he believes, whether
it be rational or irrational,
then nobody is in a position to distinguish between
warranted and unwarranted truth claims

or to urge his own truth claims with any moral force.

Valid chains of reasoning might occur, but nobody --
including the naturalist making truth claims for
naturalism -- would be in a position to benefit from them.

Reppert implies all of this when he talks about the
problem of knowing that one is rational,
but it seems to me that his case would be strengthened
by bringing it out more clearly.

( Donald T. Williams , Toccoa Falls College )

Darwinists attempt to use science to show that our world and its inhabitants
can be fully explained as the product of a mindless, purposeless system
of physics and chemistry.
But Lewis claimed in his argument from reason that if such materialism
or naturalism were true
then scientific reasoning itself could not be trusted.

Lewis's arguments have been too often dismissed.

( from goodreads )

( sample )