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5. Theory of Logic / H. Proof Systems / 6. Sequent Calculi

[proof were every step is a proof and not just a formula]

5 ideas
Each line of a sequent calculus is a conclusion of previous lines, each one explicitly recorded [Bostock]
A sequent calculus is good for comparing proof systems [Bostock]
We can build one expanding sequence, instead of a chain of deductions [Burgess]
The sequent calculus makes it possible to have proof without transitivity of entailment [Burgess]
We can build proofs just from conclusions, rather than from plain formulae [Sider]