Thursday, June 25, 2009

Why Christianity and Islam cannot both be true

A redated post.

If two statements contradict one another, one must be true and the other false. That is the most fundamental law of logic. Thus the claims:
1) "God' final revelation to man is in the Qu'ran, where it is taught that Jesus never died by crucifixion."
conflicts with
2) "Christ's death on the cross atones for our sins."
1 logically entails
1A) Jesus did not die by crucifixion.
While 2 logically entials
2A) Jesus died by crucifixion.
Thus the central claims of Islam and the central claims of Christianity cannot both be true. The issue, by the way, is a factual issue. It does not even involve the supernatural.

12 comments:

Ilíon said...

Islam itself, and conseguently the general Moslem, is as antipathetic to actual logical reasoning as is the typical 'atheist' or "Darwinist."

brian said...

The Koran abrogates all previous revelations. It also abrogates itself: http://isupporttheresistance.blogspot.com/2007/11/taqiyya-lies-and-muslim-propagana.html

Ilíon said...

VR: "If two statements contradict one another, one must be true and the other false. That is the most fundamental law of logic. ..."

What you said is not what you mean.

DeanAZ said...

"If two statements contradict one another, one must be true and the other false. "

Of course, it could be the case that they are both false, and again, I'm sure that is not what you meant.

Victor Reppert said...

No. If they are genuine contradictories, as opposed to contraries, then one has to be true and the other false. If you look at the square of opposition, you can see that this is the case.

From the Internet Encyclopedia of Philosophy:

Firstly, A and O propositions are contradictory, as are E and I propositions. Propositions are contradictory when the truth of one implies the falsity of the other, and conversely.

http://www.iep.utm.edu/s/sqr-opp.htm

Ilíon said...

VR: "No. If they are genuine contradictories, as opposed to contraries, then one has to be true and the other false."

Sure. Except that people rarely use the words like that; even my old Webster's from the early 1960s secondarily defines 'contradiction' in terms of 'contrariness.'

Else, why speak of exhaustive and mutually exclusive statements or worry about excluded middles?

Ilíon said...

After all, of some hypothetical situation which may logically (and exhaustively) be described or explained by one of three three mutually exclusive propositions, would one *really* say that none of the statements contradict the other two?

Ilíon said...

Even the two seemingly simple opposing statements --
1) Christian claim: "Jesus was executed on a cross"
2) Islamic claim: "Jesus was not executed on a cross"
are not really simple propositions, but are rather complex propositions --
1) Christian claim: "There was a man named Jesus AND he was executed on a cross"
2) Islamic claim: "There was a man named Jesus (whom some say was executed on a cross) BUT he was not executed on a cross"

It is a logical possibility that the name 'Jesus' (or 'Issa' as the Moslems call him) does not refer to any man who ever lived. And were it true that Jesus never lived, then both the Christian and the Moslem claims above are false.

One Brow said...

Dr. Reppert,

I think Ilion is correct in his analysis that the situation you presented was not a true logical contradiction.

Shackleman said...

I've said it before but it's worth repeating:

"When one points to the moon, stop staring at one's hand."

I have no problem when one points out a syntactical issue. It happens. But lets not get stuck there---point it out and move on.

Ilíon said...

But then, you also seek to brush off semantics.

How then shall we communicate if we do not take care first to semantics and them to syntax?

Are you so care-free of syntax when dealing with computer languages?

Ilíon said...

And, by the way, the point is a point of semantics.