On what grounds are the three classic laws of thought rendered 'true'? Is there a more fundamental law which enables us to see the law of identity, the law of excluded middle and the law of non-contradiction as true? If not, how can we claim that they are anything more than guidelines for thought?

The last two of your three questions suggest this: We can't properly regard some law P as true (rather than merely as a guideline for thought) unless there's some more fundamental law Q that enables us to see that P is true. But presumably Q must also be something we properly regard as true, in which case your suggestion implies an infinite regress: there must be some more fundamental law R that enables us to see that Q is true. Likewise for R, and so on. This infinite regress may be a good reason to reject your suggestion. Why must our properly regarding P as true depend on there being some more fundamental law?

In any case, I can't see how there could be any law more fundamental than the law of non-contradiction (LNC). Let F be any such law. If the claim "F is more fundamental than LNC" is meaningful (and it may not be), then it conflicts with the claim "F isn't more fundamental than LNC" -- but that reasoning, of course, depends on LNC.

Read another response by Stephen Maitzen
Read another response about Logic