Logic Systems
System T
(1) □ p → p
(2) □ (p → q) → (□ p → □ q)
System B (Brouwerian)
(3) p → □ ◊ p
System S4 (Lewis)
(4) □ p → □ □ p
System S5 (Lewis)
(5) ◊ p → □ ◊ p
System T
(1) □ p → p
(2) □ (p → q) → (□ p → □ q)
System B (Brouwerian)
(3) p → □ ◊ p
System S4 (Lewis)
(4) □ p → □ □ p
System S5 (Lewis)
(5) ◊ p → □ ◊ p