by Brian Bosse, Copyright June 27, 2009, all rights reserved. 1199 views
The ground for rationality is God in the sense that rationality is the way God thinks. Logic is mankind's attempt to model this thinking of God. Yet far too often we hear people deprecate logic as something merely human. Granted, our modeling of God's thinking is fallible. Yet, our modeling reflects the rational argumentation explicitly utilized in the God-breathed Scriptures. This post illustrates the use of two of the most fundamental laws of logic - modus ponens and modus tollens.
Modus Ponens
The logical law of modus ponens states that if we are given an implication and the antecedent of the implication as premises, then we may conclude the consequence of the implication. In other words:
Premise 1: If A, then B.
Premise 2: A.
Conclusion: B.
Premise 1: If you do believe, then you will be saved.
Premise 2: You do believe.
Conclusion: You will be saved.
One Biblical argument illustrating this deductive process is found in Romans 5:8-10. Here is the text as found in the NASB:
(8) But God demonstrates His own love toward us, in that while we were yet sinners, Christ died for us. (9) Much more then, having now been justified by His blood, we shall be saved from the wrath of God through Him. (10) For if while we were enemies we were reconciled to God through the death of His Son, much more, having been reconciled, we shall be saved by His life.
Verse 10 is the justification for the conclusion "we shall be saved from the wrath of God through Him" found in verse 9b. Verse 10 is an implication, and verses 8 and 9a make up the antecedent of the implication. Verse 9b is the necessary conclusion reached by the law of modus ponens. Here is how it looks:
Premise 1: If while we were enemies we were reconciled to God through the death of His Son,…, then we shall be saved by His life (verse 10).
Premise 2: While we were enemies we were reconciled to God through the death of His Son. (This is what is meant by verses 8 and 9a. "While we were yet sinners" corresponds to "while we were enemies," and "Christ died for us…having been justified by His blood" corresponds to "we were reconciled to God through the death of His Son.")
Conclusion: We shall be saved by His life. (This corresponds to 9b which says, "we shall be saved from the wrath of God through Him.")
Modus Tollens
The logical law of modus tollens states that if we are given an implication and the negation of the consequence of the implication as premises, then we may conclude the negation of the antecedent of the implication. In other words:
Premise 1: If A, then B.
Premise 2: ¬B.
Conclusion: ¬A.
Premise 1: If you do believe, then you will be saved.
Premise 2: You will not be saved.
Conclusion: You do not believe.
One Biblical argument illustrating this deductive argument is found in 1 Corinthians 2:8 which reads in the ESV:
None of the rulers of this age understood this, for if they had, they would not have crucified the Lord of glory.
This is a straightforward deductive argument with an implied premise. Here is the argument:
Premise 1: If the rulers of this age understood this, then they would not have crucified the Lord of glory.
Premise 2: They did crucify the Lord of Glory. (Implied in the argument.)
Conclusion: The rulers of this age did not understand this.
There are numerous such arguments found throughout Scripture. The point is that the God-breathed Scriptures themselves presuppose these logical laws. These logical laws find their origination in God Himself, and are not some human concoction.