The die is less than 4 only if it is odd
L:
the die is less than 4
; O:
the die is odd
T
F
L
T
F
O
¬ L
¬ L ← ¬ O
¬ L ← ¬ O
limit possibilities ruled
out by ¬ L to those
where O is
F
extend possibilities left open
by ¬ L to include all those
where O is
T