On 6/18/2015 8:35 AM, John Clark wrote:
On Wed, Jun 17, 2015 Bruce Kellett <[email protected]
<mailto:[email protected]>> wrote:
> '2+2=4' is a tautology by virtue of the meanings of the terms involved.
Yes, and E=MC^2 is a tautology too as is every correct mathematical equation. For this
reason 2+2=5 is NOT a tautology.
This is gitting muddled. '2+2=4' is a tautology if the symbols are given their meaning by
Peano's axioms or similar axiom set and rules of inference. If the symbols are
interpreted as the size of specific physical sets, e.g. my example of fathers and sons,
it's not a tautology. Similarly, in it's usual interpretation as referring to measurable
physical quantities, E=mc^2 is not a tautology.
Brent
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