Theorem frind 27633

Description: The principle of founded induction. Theorem 4.4 of Don Monk's notes (see frmin 27632). 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 27597 and tfi 6463, 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 3734	. . . . . . 7 |- ( A C_ B <-> ( A \ B ) = (/) )
2	1	necon3bbii 2637	. . . . . 6 |- ( -. A C_ B <-> ( A \ B ) =/= (/) )
3		difss 3480	. . . . . . 7 |- ( A \ B ) C_ A
4		frmin 27632	. . . . . . . . 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 3335	. . . . . . . . . . . . 13 |- ( y e. ( A \ B ) <-> ( y e. A /\ -. y e. B ) )
6	5	anbi1i 690	. . . . . . . . . . . 12 |- ( ( y e. ( A \ B ) /\ Pred ( R , ( A \ B ) , y ) = (/) ) <-> ( ( y e. A /\ -. y e. B ) /\ Pred ( R , ( A \ B ) , y ) = (/) ) )
7		anass 644	. . . . . . . . . . . 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 448	. . . . . . . . . . . . . 14 |- ( ( -. y e. B /\ Pred ( R , ( A \ B ) , y ) = (/) ) <-> ( Pred ( R , ( A \ B ) , y ) = (/) /\ -. y e. B ) )
9		indif2 3590	. . . . . . . . . . . . . . . . . 18 |- ( ( `' R " { y } ) i^i ( A \ B ) ) = ( ( ( `' R " { y } ) i^i A ) \ B )
10		df-pred 27554	. . . . . . . . . . . . . . . . . . 19 |- Pred ( R , ( A \ B ) , y ) = ( ( A \ B ) i^i ( `' R " { y } ) )
11		incom 3540	. . . . . . . . . . . . . . . . . . 19 |- ( ( A \ B ) i^i ( `' R " { y } ) ) = ( ( `' R " { y } ) i^i ( A \ B ) )
12	10, 11	eqtri 2461	. . . . . . . . . . . . . . . . . 18 |- Pred ( R , ( A \ B ) , y ) = ( ( `' R " { y } ) i^i ( A \ B ) )
13		df-pred 27554	. . . . . . . . . . . . . . . . . . . 20 |- Pred ( R , A , y ) = ( A i^i ( `' R " { y } ) )
14		incom 3540	. . . . . . . . . . . . . . . . . . . 20 |- ( A i^i ( `' R " { y } ) ) = ( ( `' R " { y } ) i^i A )
15	13, 14	eqtri 2461	. . . . . . . . . . . . . . . . . . 19 |- Pred ( R , A , y ) = ( ( `' R " { y } ) i^i A )
16	15	difeq1i 3467	. . . . . . . . . . . . . . . . . 18 |- ( Pred ( R , A , y ) \ B ) = ( ( ( `' R " { y } ) i^i A ) \ B )
17	9, 12, 16	3eqtr4i 2471	. . . . . . . . . . . . . . . . 17 |- Pred ( R , ( A \ B ) , y ) = ( Pred ( R , A , y ) \ B )
18	17	eqeq1i 2448	. . . . . . . . . . . . . . . 16 |- ( Pred ( R , ( A \ B ) , y ) = (/) <-> ( Pred ( R , A , y ) \ B ) = (/) )
19		ssdif0 3734	. . . . . . . . . . . . . . . 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 690	. . . . . . . . . . . . . 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 689	. . . . . . . . . . . 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 2742	. . . . . . . . . 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 2759	. . . . . . . . . 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 671	. . . . . 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 710	. 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 750	. 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 3370	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 1364   e. wcel 1761   =/= wne 2604   A.wral 2713   E.wrex 2714   \ cdif 3322   i^i cin 3324   C_ wss 3325   (/)c0 3634   {csn 3874   Fr wfr 4672   Se wse 4673   `'ccnv 4835   "cima 4839   Predcpred 27553

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1596  ax-4 1607  ax-5 1675  ax-6 1713  ax-7 1733  ax-8 1763  ax-9 1765  ax-10 1780  ax-11 1785  ax-12 1797  ax-13 1948  ax-ext 2422  ax-rep 4400  ax-sep 4410  ax-nul 4418  ax-pow 4467  ax-pr 4528  ax-un 6371  ax-inf2 7843

This theorem depends on definitions:  df-bi 185  df-or 370  df-an 371  df-3or 961  df-3an 962  df-tru 1367  df-ex 1592  df-nf 1595  df-sb 1706  df-eu 2261  df-mo 2262  df-clab 2428  df-cleq 2434  df-clel 2437  df-nfc 2566  df-ne 2606  df-ral 2718  df-rex 2719  df-reu 2720  df-rab 2722  df-v 2972  df-sbc 3184  df-csb 3286  df-dif 3328  df-un 3330  df-in 3332  df-ss 3339  df-pss 3341  df-nul 3635  df-if 3789  df-pw 3859  df-sn 3875  df-pr 3877  df-tp 3879  df-op 3881  df-uni 4089  df-iun 4170  df-br 4290  df-opab 4348  df-mpt 4349  df-tr 4383  df-eprel 4628  df-id 4632  df-po 4637  df-so 4638  df-fr 4675  df-se 4676  df-we 4677  df-ord 4718  df-on 4719  df-lim 4720  df-suc 4721  df-xp 4842  df-rel 4843  df-cnv 4844  df-co 4845  df-dm 4846  df-rn 4847  df-res 4848  df-ima 4849  df-iota 5378  df-fun 5417  df-fn 5418  df-f 5419  df-f1 5420  df-fo 5421  df-f1o 5422  df-fv 5423  df-om 6476  df-recs 6828  df-rdg 6862  df-pred 27554  df-trpred 27611

This theorem is referenced by:  frindi  27634  frinsg  27635