I'm sure this question must have a simple clarification, but I am largely unfamiliar with the branches of formal logic and not sure where to look for it.

We know that "All bachelors are unmarried men" is among the classic examples of an analytical truth. I note that in one question at this site that it is even given as a "tenseless" proposition in contrast to those requiring temporal operators.

At the same time, this very example is historically not the case. Since "marriage" was once quite strictly defined as a sacrament between a man and a woman, we now have any number of "married bachelors."

As far as I recall, this was not the kind of issue raised in, say, Quine's "Two Dogmas of Empiricism," nor would it seem to me be readily fixed by adding temporal conditions to an entire proposition.

The problem in this case is that "bachelor" remains fixed while "marriage" changes. The subject and predicate cannot, in a sense, change "tenses" at the same rate. Nor could any subject and predicate. Breaking them apart and adding different temporal operators in an attempt to different terms would only seem to lead to an infinite regress.

This seems perhaps closer to Hegel's "historical" approach, in which the law of contradiction must be jettisoned if we accept the reality of motion. Or simply an ultimate capitulation to induction and probability.It also sounds like the kind of thing late Wittgenstein might assert, though I have only a passing familiarity with his work.

I guess my question is: does formal logic have a simple fix for this? Is there something obvious I am missing? Or does this historical stance simply assert a "material" (for lack of a better word) limit to "logic" no matter how it is expressed? Again, sorry but formal demonstrations will probably be beyond my present grasp.

  • 1
    Bachelor was originally a guild rank, which was applicable to married men. And in the modern version of all the terms used around me, though presumably not around you, there are still no married bachelors, as everyone had already restricted bachelor to those not seriously attached, whether the couple was legally married, or even potentially legally marriageable, before the sense of marriage shifted. – user9166 Feb 8 '16 at 17:57
  • 1
    So all the definitions involved have shifted. As definitions simply do. What is the point? Logic is an approximation, and the approximation gotten by adding temporal and contextual distinctions ad hoc is simply good enough. – user9166 Feb 8 '16 at 17:57
  • 2
    It is not a limit of logic, it is a presumption about how closely logic can be expected to match grammar and meaning. It can only really do so in a 'frozen field' like mathematics, or in idealized instants when we all think we agree on the meanings of everything. When it comes down to it, there are no statable propositions that are actually about anything and really behave like logic. From any really modern point of view, ambiguity reigns, and definitions are maintained by usage and feedback. – user9166 Feb 8 '16 at 18:04
  • 1
    It is like asking whether measurement tolerances are a limitation of physics. Well, no. They are a limitation of every potential application of physics to a real problem, or any interpretation of actual data in terms of a physical theory. But that is not a limitation of physics per se. – user9166 Feb 8 '16 at 18:06
  • 2
    The need to carefully define your predicates has always been a challenging issue for formal logic. Also, the need to be careful what premisses you accept is a big deal as well. "All bachelors are unmarried men" is given as an example for explanitory purposes, but here it is accepted as a premise for the argument. All of the trouble stems from trying to get around the issues that arise from accepting premises that do not describe reality very well. – Cort Ammon Feb 8 '16 at 18:17

"Bachelor are unmarried men" is an analytic proposition given the contemporary meaning of "bachelor" and "married". Words had different meanings at different times but it only follows that the same sentence was expressing a different proposition, not that the proposition that it expresses today is not analytic. Since formal logic is concerned by propositions, not sentences, it doesn't have to bother with this issue.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.