> >> >> >No. P may be false and validly imply true Q. > >> >> > >> >> I don't follow this. If P is false then any Q demonstrated of P is > >> >> false too. > >> > > >> >Let P = Margaret Thatcher is a man, and all men are politicians. > >> >Let Q = Margaret Thatcher is a politician. > >> > > >> >P is false, and validly implies Q, which is true. > >> > >> Well sure but you're using compound predicates which are false to > >> begin with
I think you mean "compound sentences" or "compound propositions".
> >> and don't really imply Q except to the extent they're > >> false.
No. The validity of the argument does not rest on the premise being false.
> >> If I were simply to say "Margaret Thatcher is a male politician" > >> the effect would be exactly the same.
This is correct. "Margaret Thatcher is a male politician" follows from "Margaret Thatcher is a man, and all men are politicians".
Futhermore, the inference "Margaret Thatcher is a male politician, therefore Margaret Thatcher is a politician" is a valid inference, with a false premise and a true conclusion, and the validity of the inference does not rest on the falseness of the premise.
> > Not to anyone who knows anything about logic.
Just because a lot of what Lester says is wrong, doesn't mean everything he says is wrong. Don't let him stampede you into pre-emptory dismissal of everything he says, as tempting as that might be.
> But apparently to anyone who knows nothing about truth. > > >> The proposition is just false.
True. The proposition P is false, and "Margaret Thatcher is a male politician" is false.
> >> Q may or may not be true
Q is true.
> >> but not because P is false.
> >It is the compound proposition "If P then Q" whose truth is under > >consideration, and for the P and Q given, "If P then Q" is true.
'Even the crows on the roofs caw about the nature of conditionals.'