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Not All Good Arguments Are Logically Sound

Some interesting thoughts from James Gray on whether all good arguments are logically sound. Understanding why helps us appreciate good arguments.

Proof that not all arguments are logically sound
An argument against the belief that all good arguments are logically sound is the following:

  1. At least some good scientific theories were proven to be false.
  2. If at least some good scientific theories could proven to be false, then not all good arguments are logically sound.
  3. Therefore, not all good argument are logically sound.

Premise 1 – Is it true that “at least some good scientific theories were proven to be false?” Yes. For example, I think Newton’s theory of physics is a good example. It was believed that Newton’s theory of physics was complete and could predict any physical motion, but it failed to predict the motion of Mercury. However, Einstein’s theory of physics was able to predict the motion of Mercury and is now considered to be a better (and more complete) theory of physics.

Premise 2 – Is it true that “if at least some good scientific theories could proven to be false, then not all good arguments are logically sound?” Yes. Scientists give good arguments in favor of good scientific theories. If all good scientific theories are proven to be true by sound arguments, then they can’t be proven to be false. Sound arguments would guarantee the theories are true because the premises would be true and the arguments for the theories would be valid—valid arguments can’t have true premises and false conclusions at the same time.

Given these two premises, the conclusion must be true (that not all good arguments are logically sound). Why? Because this argument uses a valid logical form. The logical form is “a. If a, then b. Therefore, b.” This valid logical form is well-known to be valid and is called “modus ponens.”