Theorem sb4or 1826

Description: One direction of a simplified definition of substitution when variables are distinct. Similar to sb4 1825 but stronger in intuitionistic logic. (Contributed by Jim Kingdon, 2-Feb-2018.)

Assertion

Ref	Expression
sb4or	|- ( A. x x = y \/ A. x ( [ y / x ] ph -> A. x ( x = y -> ph ) ) )

Proof of Theorem sb4or

Step	Hyp	Ref	Expression
1		equs5or 1823	. 2 |- ( A. x x = y \/ ( E. x ( x = y /\ ph ) -> A. x ( x = y -> ph ) ) )
2		nfe1 1489	. . . . . 6 |- F/ x E. x ( x = y /\ ph )
3		nfa1 1534	. . . . . 6 |- F/ x A. x ( x = y -> ph )
4	2, 3	nfim 1565	. . . . 5 |- F/ x ( E. x ( x = y /\ ph ) -> A. x ( x = y -> ph ) )
5	4	nfri 1512	. . . 4 |- ( ( E. x ( x = y /\ ph ) -> A. x ( x = y -> ph ) ) -> A. x ( E. x ( x = y /\ ph ) -> A. x ( x = y -> ph ) ) )
6		sb1 1759	. . . . 5 |- ( [ y / x ] ph -> E. x ( x = y /\ ph ) )
7	6	imim1i 60	. . . 4 |- ( ( E. x ( x = y /\ ph ) -> A. x ( x = y -> ph ) ) -> ( [ y / x ] ph -> A. x ( x = y -> ph ) ) )
8	5, 7	alrimih 1462	. . 3 |- ( ( E. x ( x = y /\ ph ) -> A. x ( x = y -> ph ) ) -> A. x ( [ y / x ] ph -> A. x ( x = y -> ph ) ) )
9	8	orim2i 756	. 2 |- ( ( A. x x = y \/ ( E. x ( x = y /\ ph ) -> A. x ( x = y -> ph ) ) ) -> ( A. x x = y \/ A. x ( [ y / x ] ph -> A. x ( x = y -> ph ) ) ) )
10	1, 9	ax-mp 5	1 |- ( A. x x = y \/ A. x ( [ y / x ] ph -> A. x ( x = y -> ph ) ) )

Syntax hints:   -> wi 4   /\ wa 103   \/ wo 703   A.wal 1346   E.wex 1485   [wsb 1755

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-io 704  ax-5 1440  ax-7 1441  ax-gen 1442  ax-ie1 1486  ax-ie2 1487  ax-8 1497  ax-10 1498  ax-11 1499  ax-i12 1500  ax-4 1503  ax-17 1519  ax-i9 1523  ax-ial 1527  ax-i5r 1528

This theorem depends on definitions:  df-bi 116  df-nf 1454  df-sb 1756

This theorem is referenced by:  sb4bor  1828  nfsb2or  1830