Logical Fallacies and You 1.5: Truth, Validity, and Soundness

I'm sorry for not posting last week, but, it was the week after Christmas and I got a bunch of new games and I was too busy playing those and fixing my sleep schedule. My circadian rhythm is a jerk.

Moving on, this week's article is not about logical fallacies, as such, but is a topic related to them. This week's topic is truth, validity, and soundness and how people who deal with logic use these terms. In common use, these terms all mean the same thing. But, they actually mean different things, although they are related. The difference mostly comes from the difference between the argument and the statements.

Truth means exactly what it sounds, whether the statements are true or not. If I say " Bulldogs are animals. All cats are animals. Therefore, all turtles are animals," that argument is true, although, it is not valid or sound. Validity, on the other hand, means the argument structure makes sense. As an example, " Bulldogs are mammals. All mammals lay eggs. Therefore, bulldogs lay eggs." This argument is valid, although it's not true or sound. A sound argument is both valid and true. As an example, " Bulldogs are dogs. Dogs are mammals. Therefore, bulldogs are mammals." This argument is true and valid, and therefore sound.
Well that's all for this week. See you next week.

~ Daniel Weber

Source: http://philosophy.lander.edu/logic/tvs.html