Theorem exmidcon 16829

Description: Excluded middle is equivalent to the form of contraposition which removes negation. Read an element of ~P 1o as being a truth value and x = 1o being that x is true. For a similar theorem, but expressed in terms of formulas rather than subsets of 1o, see dcfromcon 1494. (Contributed by Jim Kingdon, 22-Apr-2026.)

Assertion

Ref	Expression
exmidcon	|- (EXMID <-> A. x e. ~P 1o A. y e. ~P 1o ( ( -. y = 1o -> -. x = 1o ) -> ( x = 1o -> y = 1o ) ) )

Distinct variable group:   x, y

Proof of Theorem exmidcon

Step	Hyp	Ref	Expression
1		exmidexmid 4311	. . . . 5 |- (EXMID -> DECID y = 1o )
2		condc 861	. . . . 5 |- (DECID y = 1o -> ( ( -. y = 1o -> -. x = 1o ) -> ( x = 1o -> y = 1o ) ) )
3	1, 2	syl 14	. . . 4 |- (EXMID -> ( ( -. y = 1o -> -. x = 1o ) -> ( x = 1o -> y = 1o ) ) )
4	3	ralrimivw 2618	. . 3 |- (EXMID -> A. y e. ~P 1o ( ( -. y = 1o -> -. x = 1o ) -> ( x = 1o -> y = 1o ) ) )
5	4	ralrimivw 2618	. 2 |- (EXMID -> A. x e. ~P 1o A. y e. ~P 1o ( ( -. y = 1o -> -. x = 1o ) -> ( x = 1o -> y = 1o ) ) )
6		eqeq1 2241	. . . . . . . 8 |- ( x = 1o -> ( x = 1o <-> 1o = 1o ) )
7	6	notbid 673	. . . . . . 7 |- ( x = 1o -> ( -. x = 1o <-> -. 1o = 1o ) )
8	7	imbi2d 230	. . . . . 6 |- ( x = 1o -> ( ( -. y = 1o -> -. x = 1o ) <-> ( -. y = 1o -> -. 1o = 1o ) ) )
9	6	imbi1d 231	. . . . . 6 |- ( x = 1o -> ( ( x = 1o -> y = 1o ) <-> ( 1o = 1o -> y = 1o ) ) )
10	8, 9	imbi12d 234	. . . . 5 |- ( x = 1o -> ( ( ( -. y = 1o -> -. x = 1o ) -> ( x = 1o -> y = 1o ) ) <-> ( ( -. y = 1o -> -. 1o = 1o ) -> ( 1o = 1o -> y = 1o ) ) ) )
11	10	ralbidv 2544	. . . 4 |- ( x = 1o -> ( A. y e. ~P 1o ( ( -. y = 1o -> -. x = 1o ) -> ( x = 1o -> y = 1o ) ) <-> A. y e. ~P 1o ( ( -. y = 1o -> -. 1o = 1o ) -> ( 1o = 1o -> y = 1o ) ) ) )
12		id 19	. . . 4 |- ( A. x e. ~P 1o A. y e. ~P 1o ( ( -. y = 1o -> -. x = 1o ) -> ( x = 1o -> y = 1o ) ) -> A. x e. ~P 1o A. y e. ~P 1o ( ( -. y = 1o -> -. x = 1o ) -> ( x = 1o -> y = 1o ) ) )
13		1oex 6657	. . . . . 6 |- 1o e. _V
14	13	pwid 3689	. . . . 5 |- 1o e. ~P 1o
15	14	a1i 9	. . . 4 |- ( A. x e. ~P 1o A. y e. ~P 1o ( ( -. y = 1o -> -. x = 1o ) -> ( x = 1o -> y = 1o ) ) -> 1o e. ~P 1o )
16	11, 12, 15	rspcdva 2928	. . 3 |- ( A. x e. ~P 1o A. y e. ~P 1o ( ( -. y = 1o -> -. x = 1o ) -> ( x = 1o -> y = 1o ) ) -> A. y e. ~P 1o ( ( -. y = 1o -> -. 1o = 1o ) -> ( 1o = 1o -> y = 1o ) ) )
17		eqid 2234	. . . . . . 7 |- 1o = 1o
18		ax-in2 620	. . . . . . . . 9 |- ( -. -. y = 1o -> ( -. y = 1o -> -. 1o = 1o ) )
19	18	adantr 276	. . . . . . . 8 |- ( ( -. -. y = 1o /\ ( ( -. y = 1o -> -. 1o = 1o ) -> ( 1o = 1o -> y = 1o ) ) ) -> ( -. y = 1o -> -. 1o = 1o ) )
20		simpr 110	. . . . . . . 8 |- ( ( -. -. y = 1o /\ ( ( -. y = 1o -> -. 1o = 1o ) -> ( 1o = 1o -> y = 1o ) ) ) -> ( ( -. y = 1o -> -. 1o = 1o ) -> ( 1o = 1o -> y = 1o ) ) )
21	19, 20	mpd 13	. . . . . . 7 |- ( ( -. -. y = 1o /\ ( ( -. y = 1o -> -. 1o = 1o ) -> ( 1o = 1o -> y = 1o ) ) ) -> ( 1o = 1o -> y = 1o ) )
22	17, 21	mpi 15	. . . . . 6 |- ( ( -. -. y = 1o /\ ( ( -. y = 1o -> -. 1o = 1o ) -> ( 1o = 1o -> y = 1o ) ) ) -> y = 1o )
23	22	expcom 116	. . . . 5 |- ( ( ( -. y = 1o -> -. 1o = 1o ) -> ( 1o = 1o -> y = 1o ) ) -> ( -. -. y = 1o -> y = 1o ) )
24	23	ralimi 2607	. . . 4 |- ( A. y e. ~P 1o ( ( -. y = 1o -> -. 1o = 1o ) -> ( 1o = 1o -> y = 1o ) ) -> A. y e. ~P 1o ( -. -. y = 1o -> y = 1o ) )
25		exmidnotnotr 16828	. . . 4 |- (EXMID <-> A. y e. ~P 1o ( -. -. y = 1o -> y = 1o ) )
26	24, 25	sylibr 134	. . 3 |- ( A. y e. ~P 1o ( ( -. y = 1o -> -. 1o = 1o ) -> ( 1o = 1o -> y = 1o ) ) -> EXMID )
27	16, 26	syl 14	. 2 |- ( A. x e. ~P 1o A. y e. ~P 1o ( ( -. y = 1o -> -. x = 1o ) -> ( x = 1o -> y = 1o ) ) -> EXMID )
28	5, 27	impbii 126	1 |- (EXMID <-> A. x e. ~P 1o A. y e. ~P 1o ( ( -. y = 1o -> -. x = 1o ) -> ( x = 1o -> y = 1o ) ) )

Syntax hints:   -. wn 3   -> wi 4   /\ wa 104   <-> wb 105  DECID wdc 842   = wceq 1398   e. wcel 2205   A.wral 2522   ~Pcpw 3671  EXMIDwem 4309   1oc1o 6642

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 619  ax-in2 620  ax-io 717  ax-5 1496  ax-7 1497  ax-gen 1498  ax-ie1 1542  ax-ie2 1543  ax-8 1553  ax-10 1554  ax-11 1555  ax-i12 1556  ax-bndl 1558  ax-4 1559  ax-17 1575  ax-i9 1579  ax-ial 1583  ax-i5r 1584  ax-13 2207  ax-14 2208  ax-ext 2216  ax-sep 4230  ax-nul 4238  ax-pow 4289  ax-pr 4324  ax-un 4556

This theorem depends on definitions:  df-bi 117  df-stab 839  df-dc 843  df-tru 1401  df-fal 1404  df-nf 1510  df-sb 1812  df-clab 2221  df-cleq 2227  df-clel 2230  df-nfc 2375  df-ne 2415  df-ral 2527  df-rex 2528  df-rab 2531  df-v 2817  df-dif 3215  df-un 3217  df-in 3219  df-ss 3226  df-nul 3511  df-pw 3673  df-sn 3697  df-pr 3698  df-uni 3917  df-tr 4211  df-exmid 4310  df-iord 4489  df-on 4491  df-suc 4494  df-1o 6649

This theorem is referenced by: (None)