Sunday, September 20, 2009

A few Thoughts About Logical Truth & Contingent Statements

What are logical truths? "Logical truths are sentences that are true simply in virtue of their logical form. One example of a logical truth in classical logic is the law of non- contradiction, ~ ( p ~ p) ( not both p and not p, or colloquially, it can't be the case that a sentence and its negation are both true)." (Jennifer Fisher, On the Philosophy of Logic, 55)

In my Logic classes I am working to get this point across to students. Some are having a tough time grasping the idea of logical form. It's important to understand this to grasp the idea that logical truth has nothing to do with anthropological or sociological studies regarding the history of ideas. Such as, e.g., how some particular was formed and has been transmitted.

"Contingent sentences are sentences that are made true or false by the way the world is.... These truths are said to be contingent because they might have been otherwise." (Fisher) For example, ‘ John Piippo has a dog’ is false, but it might have been otherwise. I might have a dog, and if I did have a dog, then the sentence would be true.

Even though the truth or falsity of contingent statements depend on the way the world is, they are in no way dependent on sociological or psychological studies as to how John came to believe that the sentence "John has a dog" is false. Nor are they dependent on John's psychological condition when he claims that "John has a dog" is false. So while the truth or falsity of contingent statements depends on some fact or facts about the world, this does not concern the genesis of our ideas about worldly facts. It's important to maintain these distinctions so as not to fall prey to the genetic fallacy.