Theorem frind 27707

Description: The principle of founded induction. Theorem 4.4 of Don Monk's notes (see frmin 27706). This principle states that if B is a subclass of a founded class A with the property that every element of B whose initial segment is included in A is itself equal to A. Compare wfi 27671 and tfi 6467, which are special cases of this theorem that do not require the axiom of infinity to prove. (Contributed by Scott Fenton, 6-Feb-2011.) (Revised by Mario Carneiro, 26-Jun-2015.)

Assertion

Ref	Expression
frind	|- ( ( ( R Fr A /\ R Se A ) /\ ( B C_ A /\ A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) ) ) -> A = B )

Distinct variable groups:   y, A   y, B   y, R

Proof of Theorem frind

Step	Hyp	Ref	Expression
1		ssdif0 3740	. . . . . . 7 |- ( A C_ B <-> ( A \ B ) = (/) )
2	1	necon3bbii 2642	. . . . . 6 |- ( -. A C_ B <-> ( A \ B ) =/= (/) )
3		difss 3486	. . . . . . 7 |- ( A \ B ) C_ A
4		frmin 27706	. . . . . . . . 9 |- ( ( ( R Fr A /\ R Se A ) /\ ( ( A \ B ) C_ A /\ ( A \ B ) =/= (/) ) ) -> E. y e. ( A \ B ) Pred ( R , ( A \ B ) , y ) = (/) )
5		eldif 3341	. . . . . . . . . . . . 13 |- ( y e. ( A \ B ) <-> ( y e. A /\ -. y e. B ) )
6	5	anbi1i 695	. . . . . . . . . . . 12 |- ( ( y e. ( A \ B ) /\ Pred ( R , ( A \ B ) , y ) = (/) ) <-> ( ( y e. A /\ -. y e. B ) /\ Pred ( R , ( A \ B ) , y ) = (/) ) )
7		anass 649	. . . . . . . . . . . 12 |- ( ( ( y e. A /\ -. y e. B ) /\ Pred ( R , ( A \ B ) , y ) = (/) ) <-> ( y e. A /\ ( -. y e. B /\ Pred ( R , ( A \ B ) , y ) = (/) ) ) )
8		ancom 450	. . . . . . . . . . . . . 14 |- ( ( -. y e. B /\ Pred ( R , ( A \ B ) , y ) = (/) ) <-> ( Pred ( R , ( A \ B ) , y ) = (/) /\ -. y e. B ) )
9		indif2 3596	. . . . . . . . . . . . . . . . . 18 |- ( ( `' R " { y } ) i^i ( A \ B ) ) = ( ( ( `' R " { y } ) i^i A ) \ B )
10		df-pred 27628	. . . . . . . . . . . . . . . . . . 19 |- Pred ( R , ( A \ B ) , y ) = ( ( A \ B ) i^i ( `' R " { y } ) )
11		incom 3546	. . . . . . . . . . . . . . . . . . 19 |- ( ( A \ B ) i^i ( `' R " { y } ) ) = ( ( `' R " { y } ) i^i ( A \ B ) )
12	10, 11	eqtri 2463	. . . . . . . . . . . . . . . . . 18 |- Pred ( R , ( A \ B ) , y ) = ( ( `' R " { y } ) i^i ( A \ B ) )
13		df-pred 27628	. . . . . . . . . . . . . . . . . . . 20 |- Pred ( R , A , y ) = ( A i^i ( `' R " { y } ) )
14		incom 3546	. . . . . . . . . . . . . . . . . . . 20 |- ( A i^i ( `' R " { y } ) ) = ( ( `' R " { y } ) i^i A )
15	13, 14	eqtri 2463	. . . . . . . . . . . . . . . . . . 19 |- Pred ( R , A , y ) = ( ( `' R " { y } ) i^i A )
16	15	difeq1i 3473	. . . . . . . . . . . . . . . . . 18 |- ( Pred ( R , A , y ) \ B ) = ( ( ( `' R " { y } ) i^i A ) \ B )
17	9, 12, 16	3eqtr4i 2473	. . . . . . . . . . . . . . . . 17 |- Pred ( R , ( A \ B ) , y ) = ( Pred ( R , A , y ) \ B )
18	17	eqeq1i 2450	. . . . . . . . . . . . . . . 16 |- ( Pred ( R , ( A \ B ) , y ) = (/) <-> ( Pred ( R , A , y ) \ B ) = (/) )
19		ssdif0 3740	. . . . . . . . . . . . . . . 16 |- ( Pred ( R , A , y ) C_ B <-> ( Pred ( R , A , y ) \ B ) = (/) )
20	18, 19	bitr4i 252	. . . . . . . . . . . . . . 15 |- ( Pred ( R , ( A \ B ) , y ) = (/) <-> Pred ( R , A , y ) C_ B )
21	20	anbi1i 695	. . . . . . . . . . . . . 14 |- ( ( Pred ( R , ( A \ B ) , y ) = (/) /\ -. y e. B ) <-> ( Pred ( R , A , y ) C_ B /\ -. y e. B ) )
22	8, 21	bitri 249	. . . . . . . . . . . . 13 |- ( ( -. y e. B /\ Pred ( R , ( A \ B ) , y ) = (/) ) <-> ( Pred ( R , A , y ) C_ B /\ -. y e. B ) )
23	22	anbi2i 694	. . . . . . . . . . . 12 |- ( ( y e. A /\ ( -. y e. B /\ Pred ( R , ( A \ B ) , y ) = (/) ) ) <-> ( y e. A /\ ( Pred ( R , A , y ) C_ B /\ -. y e. B ) ) )
24	6, 7, 23	3bitri 271	. . . . . . . . . . 11 |- ( ( y e. ( A \ B ) /\ Pred ( R , ( A \ B ) , y ) = (/) ) <-> ( y e. A /\ ( Pred ( R , A , y ) C_ B /\ -. y e. B ) ) )
25	24	rexbii2 2747	. . . . . . . . . 10 |- ( E. y e. ( A \ B ) Pred ( R , ( A \ B ) , y ) = (/) <-> E. y e. A ( Pred ( R , A , y ) C_ B /\ -. y e. B ) )
26		rexanali 2764	. . . . . . . . . 10 |- ( E. y e. A ( Pred ( R , A , y ) C_ B /\ -. y e. B ) <-> -. A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) )
27	25, 26	bitri 249	. . . . . . . . 9 |- ( E. y e. ( A \ B ) Pred ( R , ( A \ B ) , y ) = (/) <-> -. A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) )
28	4, 27	sylib 196	. . . . . . . 8 |- ( ( ( R Fr A /\ R Se A ) /\ ( ( A \ B ) C_ A /\ ( A \ B ) =/= (/) ) ) -> -. A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) )
29	28	ex 434	. . . . . . 7 |- ( ( R Fr A /\ R Se A ) -> ( ( ( A \ B ) C_ A /\ ( A \ B ) =/= (/) ) -> -. A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) ) )
30	3, 29	mpani 676	. . . . . 6 |- ( ( R Fr A /\ R Se A ) -> ( ( A \ B ) =/= (/) -> -. A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) ) )
31	2, 30	syl5bi 217	. . . . 5 |- ( ( R Fr A /\ R Se A ) -> ( -. A C_ B -> -. A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) ) )
32	31	con4d 105	. . . 4 |- ( ( R Fr A /\ R Se A ) -> ( A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) -> A C_ B ) )
33	32	imp 429	. . 3 |- ( ( ( R Fr A /\ R Se A ) /\ A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) ) -> A C_ B )
34	33	adantrl 715	. 2 |- ( ( ( R Fr A /\ R Se A ) /\ ( B C_ A /\ A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) ) ) -> A C_ B )
35		simprl 755	. 2 |- ( ( ( R Fr A /\ R Se A ) /\ ( B C_ A /\ A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) ) ) -> B C_ A )
36	34, 35	eqssd 3376	1 |- ( ( ( R Fr A /\ R Se A ) /\ ( B C_ A /\ A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) ) ) -> A = B )

Syntax hints:   -. wn 3   -> wi 4   /\ wa 369   = wceq 1369   e. wcel 1756   =/= wne 2609   A.wral 2718   E.wrex 2719   \ cdif 3328   i^i cin 3330   C_ wss 3331   (/)c0 3640   {csn 3880   Fr wfr 4679   Se wse 4680   `'ccnv 4842   "cima 4846   Predcpred 27627

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1591  ax-4 1602  ax-5 1670  ax-6 1708  ax-7 1728  ax-8 1758  ax-9 1760  ax-10 1775  ax-11 1780  ax-12 1792  ax-13 1943  ax-ext 2423  ax-rep 4406  ax-sep 4416  ax-nul 4424  ax-pow 4473  ax-pr 4534  ax-un 6375  ax-inf2 7850

This theorem depends on definitions:  df-bi 185  df-or 370  df-an 371  df-3or 966  df-3an 967  df-tru 1372  df-ex 1587  df-nf 1590  df-sb 1701  df-eu 2257  df-mo 2258  df-clab 2430  df-cleq 2436  df-clel 2439  df-nfc 2571  df-ne 2611  df-ral 2723  df-rex 2724  df-reu 2725  df-rab 2727  df-v 2977  df-sbc 3190  df-csb 3292  df-dif 3334  df-un 3336  df-in 3338  df-ss 3345  df-pss 3347  df-nul 3641  df-if 3795  df-pw 3865  df-sn 3881  df-pr 3883  df-tp 3885  df-op 3887  df-uni 4095  df-iun 4176  df-br 4296  df-opab 4354  df-mpt 4355  df-tr 4389  df-eprel 4635  df-id 4639  df-po 4644  df-so 4645  df-fr 4682  df-se 4683  df-we 4684  df-ord 4725  df-on 4726  df-lim 4727  df-suc 4728  df-xp 4849  df-rel 4850  df-cnv 4851  df-co 4852  df-dm 4853  df-rn 4854  df-res 4855  df-ima 4856  df-iota 5384  df-fun 5423  df-fn 5424  df-f 5425  df-f1 5426  df-fo 5427  df-f1o 5428  df-fv 5429  df-om 6480  df-recs 6835  df-rdg 6869  df-pred 27628  df-trpred 27685

This theorem is referenced by:  frindi  27708  frinsg  27709