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I often run into people who fancy themselves logical analysts or philosophers who rely on logic and reason rather than faith or other truth criteria, but they don’t seem to know much about logic. To them, “logical” means, “what I believe is true.” The people who disagree with their opinions are “illogical”. However, many of these self-proclaimed “logicians” wouldn’t recognize logical arguments if they saw them or know the difference between arguments which are logical or arguments which are fallacious. Many of them would not know the difference between deductive and inductive arguments or which parts of the arguments are the premises and which are the conclusions. They merely go by what sounds good to them or what doesn’t, what they agree with or what they don’t.
When many people use the term “valid” or any of its derivatives, they may mean “true” or “correct.” When they tell me that what I say isn’t valid, what they mean is that they don’t think what I said is true. However, people who have taken introductory logic courses know that there is a difference between “validity” and “truth”. It is possible for arguments to have validity but still have conclusions which are untrue, and it is possible for the conclusions to be true even when the argument is definitely invalid.
“Validity”, in a very tight and technical sense, has to do with the form of deductive arguments. It means that the argument is set up in such a way that the conclusion will necessarily follow from the premises. Now, the premises could be faulty, not true, and the conclusion could be true or not, but the argument is valid if and only if the conclusion follows logically from the premises. So, if the premises are true, in a valid deductive argument, the conclusion has to be true. If it is false, either one or more of the premises was false or the argument was not valid.
All this is hard to understand for those who have never studied logic or don’t know the difference between deductive arguments or inductive arguments, or the difference between premises and conclusions of arguments. It is pretty basic, however, for those who do know about logic.
One might notice, if he or she has read any of my extended debates with people who seem to worship logic and reason and think it is on their side and not mine, that I sometimes ask those “logicians” to define “validity” for me. If they ignore me or evade my question, this tells me that they do not know as much about logic as they want me and others to believe they do. (And, I can tell sometimes if people are plagiarizing from a dictionary or some website on the internet. It’s not their own words, and they can’t come up with original examples etc.)
Bis bald,
Nick
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