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I'm sorry if that question has already been asked.

Sometimes in propositional logic when proving "$\phi \rightarrow \psi$ is a tautology" using truth tables people write $\psi \Rightarrow \phi$.
But isn't that the same as proving $\psi \vDash \phi$ since truth tables are a semantic proof method?
Where's the difference between $\vDash$ and $\Rightarrow$?

Shaun
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Knogger
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