C
Catholic2003
Guest
The laws of logic are not arbitrary, but they are by convention. The majority of mathematicians follow Hilbert’s classical logic, but there are those who follow Brouwer’s intuitionism or Kronecker’s constructivism. This was a matter of some controversy in the late 1800’s (and early 1900’s).The laws of logic are not, as you suppose, only one set of basic principles among many possible sets. These laws are not selected arbitrarily or by convention. There are no “alternative logics.”
Constructive logic is an alternative logic, but it is by no means bizarre. (I would agree that relevant logic is somewhat bizarre.)Remove, say, the law of contradiction from your system and replace it with a substitute, and what do you get? Some bizarre alternative system? No. You get no system at all, and no assertion at all, for you have removed the condition of intelligible statement in any system whatever. When you change the law of contradiction what do you change to?
If you remove excluded middle, you get likewise nonsense.
In constructive logic, “A or (not A)” is not always a true statement, unless you can prove “A” or prove “(not A)”. If you can’t prove either, then how can you be sure that “A or (not A)” is true?
P.S. I also left out the various quantum logics, which attempt to model the reality of quantum physics as classical logic models the reality of classical physics.