Tableau method:
- It is a refutation method
- Does not follow the way humans reason
Σ, ϕ |= ψ if and only if Σ |= ϕ → ψ
- Prove ϕ by proving ¬ϕ
- "¬ϕ" can be interpreted as
$ϕ\Rightarrow⊥$ - ¬ϕ ... ⊥
$\Rightarrow$ ϕ -
- 横线：假设 竖线：由假设推出的结论
- E is modus ponens. I is deduction.
