Metamath Proof Explorer


Theorem frege106d

Description: If B follows A in R , then either A and B are the same or B follows A in R . Similar to Proposition 106 of Frege1879 p. 73. Compare with frege106 . (Contributed by RP, 15-Jul-2020)

Ref Expression
Hypothesis frege106d.cb
|- ( ph -> A R B )
Assertion frege106d
|- ( ph -> ( A R B \/ A = B ) )

Proof

Step Hyp Ref Expression
1 frege106d.cb
 |-  ( ph -> A R B )
2 1 orcd
 |-  ( ph -> ( A R B \/ A = B ) )