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	$$⊢\phi \to ARB$$
Assertion	frege106d	$$⊢\phi \to \left(ARB\vee A=B\right)$$

Proof

Step	Hyp	Ref	Expression
1		frege106d.cb	$$⊢\phi \to ARB$$
2	1	orcd	$$⊢\phi \to \left(ARB\vee A=B\right)$$