(intro music)
Hi, my name is Greg Ganssle,
and I'm a senior fellow[br]at the Rivendell Institute
at Yale University.
I want to start with a claim
that may seem obvious to you.
It is the claim that you cannot prove
the existence of God.
When people tell me this,
I want to ask the[br]question, "How do you know?
You just met me, maybe I can."
The response you get, if[br]you say something like that,
is that people are a little bit stunned.
They take it as obvious that you cannot
prove the existence of God.
Now, I believe, when people say this,
they are saying something true
and important philosophically.
But most people do not[br]know what's important
about this statement.
Most people think they're saying[br]something important about God.
I think they're saying something[br]important about proof.
What do most people mean when[br]they say a sentence like,
"You cannot prove the existence of God"?
Most people mean something[br]like the following:
"You cannot produce reasons or evidence
or an argument for the[br]claim that God exists,
such that your case is so strong
that it will persuade[br]everybody that God exists."
Or they mean, "You cannot[br]produce the kind of evidence
that will persuade a[br]very committed skeptic."
Of course, all of these claims are true,
but do they tell us anything about God,
or whether it's reasonable[br]to believe in God?
I think not.
What they tell us is something[br]important about proof.
Most people think about proof
in terms of a kind of argument[br]that delivers certainty.
We get this kind of proof when we look
at disciplines like mathematics, or logic.
But almost every academic discipline,
philosophy, history,[br]the physical sciences,
operates on a different kind of reasoning
than proof that delivers certainty.
This can be confusing for philosophy,
because philosophers often[br]frame their arguments
in what we call "deductive arguments."
A valid deductive argument[br]is structured such that
if the premises are true, the[br]conclusion has to be true.
So, an example you'll find in many[br]textbooks is the following.
Statement one: "All[br]human beings are mortal."
Statement two: "Socrates[br]is a human being."
Statement three: "Therefore,[br]Socrates is mortal."
You can see that if statement[br]one and statement two
are both true, statement[br]three has to be true.
That's a good example of a[br]valid deductive argument.
But in an argument like this,
most of the real work is[br]done supporting the premises.
So even though philosophers[br]often frame their
arguments in terms of deductive proofs,
most of the real work of philosophy is in
supporting the premises,
and this makes philosophy an[br]evidential discipline.
We look for evidence.
"Is the premise true?
What kinds of grounds can we bring forward
to support the premise?"
Think about it this way.
We see this kind of thing[br]on TV all of the time.
Suppose a murder has been committed.
What does the detective do?
The detective comes in and[br]picks up little bits of stuff.
And these little bits of stuff may[br]or may not become evidence.
And they investigate this evidence[br]to determine who it is who is
most likely to have killed the victim.
They never try to get 100% certainty.
They're looking to build a strong case.
And if the case is strong[br]enough to convict someone
beyond a reasonable doubt,[br]then they are successful.
So they pick up different bits of evidence
and try to fit them into[br]a story that makes sense
of the claim that a particular[br]person did the crime.
So there are two things we can notice about
the methods of a detective.
One, the case that she[br]builds is cumulative.
Very rarely will there[br]be one piece of evidence
that convicts the criminal.
There usually are many pieces of evidence.
There may be fingerprints,[br]there may be witnesses,
there may be receipts, there[br]may be all kinds of things
that locate the suspect where[br]the crime was committed.
It's a cumulative case.
Secondly, the whole approach is something
that we could call a[br]"fitting-ness approach":
how do we fit all these pieces of evidence
together into one story?
And if all the pieces of[br]evidence fit very well
into one story, they support[br]the truth of the story.
This is the way that philosophers work,
especially if we're thinking[br]about a large claim
like the claim that God exists,
or the claim that God doesn't exist.
These claims are overarching.
It's very rarely going to[br]be one piece of evidence
that strongly supports these claims.
It's going to be a number[br]of pieces working together
to justify, or ground, a particular[br]theory.
So when we do philosophy,[br]even though we might
set up our arguments[br]as deductive arguments,
most of the work is done[br]in supporting the premises
and bringing evidence[br]to bear on the claims
we want to make.
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