alternatives
		any no.	two	one	none
	any no.	renders exh. Γ ⊨ Σ Γ, Σ⋈ ⊨ ⊥		entails Γ ⊨ ψ (same)	inconsistent Γ ⊨ Γ ⊨ ⊥
	two				mutually excl. φ, φ′ ⊨ φ, φ′ ⊨ ⊥
	one			implies φ ⊨ ψ (same)	absurd φ ⊨ φ ⊨ ⊥
	none	exhaustive ⊨ Σ Σ⋈ ⊨ ⊥	jointly exh. ⊨ ψ, ψ′ ψ⋈ ⊨ ψ′	tautologous ⊨ ψ (same)
		multiple alternatives		positive conclusion	negative: no alternatives
		can replace alternatives by assumptions contradictory to them			can replace empty set of alternatives by conclusion ⊥