Theorem exmidcon 17019

Description: Excluded middle is equivalent to the form of contraposition which removes negation. Read an element of 𝒫 1_o as being a truth value and 𝑥 = 1_o being that 𝑥 is true. For a similar theorem, but expressed in terms of formulas rather than subsets of 1_o, see dcfromcon 1498. (Contributed by Jim Kingdon, 22-Apr-2026.)

Assertion

Ref	Expression
exmidcon	⊢ (EXMID ↔ ∀𝑥 ∈ 𝒫 1o∀𝑦 ∈ 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 4331	. . . . 5 ⊢ (EXMID → DECID 𝑦 = 1o)
2		condc 865	. . . . 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 2624	. . 3 ⊢ (EXMID → ∀𝑦 ∈ 𝒫 1o((¬ 𝑦 = 1o → ¬ 𝑥 = 1o) → (𝑥 = 1o → 𝑦 = 1o)))
5	4	ralrimivw 2624	. 2 ⊢ (EXMID → ∀𝑥 ∈ 𝒫 1o∀𝑦 ∈ 𝒫 1o((¬ 𝑦 = 1o → ¬ 𝑥 = 1o) → (𝑥 = 1o → 𝑦 = 1o)))
6		eqeq1 2245	. . . . . . . 8 ⊢ (𝑥 = 1o → (𝑥 = 1o ↔ 1o = 1o))
7	6	notbid 677	. . . . . . 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 2550	. . . 4 ⊢ (𝑥 = 1o → (∀𝑦 ∈ 𝒫 1o((¬ 𝑦 = 1o → ¬ 𝑥 = 1o) → (𝑥 = 1o → 𝑦 = 1o)) ↔ ∀𝑦 ∈ 𝒫 1o((¬ 𝑦 = 1o → ¬ 1o = 1o) → (1o = 1o → 𝑦 = 1o))))
12		id 19	. . . 4 ⊢ (∀𝑥 ∈ 𝒫 1o∀𝑦 ∈ 𝒫 1o((¬ 𝑦 = 1o → ¬ 𝑥 = 1o) → (𝑥 = 1o → 𝑦 = 1o)) → ∀𝑥 ∈ 𝒫 1o∀𝑦 ∈ 𝒫 1o((¬ 𝑦 = 1o → ¬ 𝑥 = 1o) → (𝑥 = 1o → 𝑦 = 1o)))
13		1oex 6689	. . . . . 6 ⊢ 1o ∈ V
14	13	pwid 3706	. . . . 5 ⊢ 1o ∈ 𝒫 1o
15	14	a1i 9	. . . 4 ⊢ (∀𝑥 ∈ 𝒫 1o∀𝑦 ∈ 𝒫 1o((¬ 𝑦 = 1o → ¬ 𝑥 = 1o) → (𝑥 = 1o → 𝑦 = 1o)) → 1o ∈ 𝒫 1o)
16	11, 12, 15	rspcdva 2934	. . 3 ⊢ (∀𝑥 ∈ 𝒫 1o∀𝑦 ∈ 𝒫 1o((¬ 𝑦 = 1o → ¬ 𝑥 = 1o) → (𝑥 = 1o → 𝑦 = 1o)) → ∀𝑦 ∈ 𝒫 1o((¬ 𝑦 = 1o → ¬ 1o = 1o) → (1o = 1o → 𝑦 = 1o)))
17		eqid 2238	. . . . . . 7 ⊢ 1o = 1o
18		ax-in2 624	. . . . . . . . 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 2613	. . . 4 ⊢ (∀𝑦 ∈ 𝒫 1o((¬ 𝑦 = 1o → ¬ 1o = 1o) → (1o = 1o → 𝑦 = 1o)) → ∀𝑦 ∈ 𝒫 1o(¬ ¬ 𝑦 = 1o → 𝑦 = 1o))
25		exmidnotnotr 17018	. . . 4 ⊢ (EXMID ↔ ∀𝑦 ∈ 𝒫 1o(¬ ¬ 𝑦 = 1o → 𝑦 = 1o))
26	24, 25	sylibr 134	. . 3 ⊢ (∀𝑦 ∈ 𝒫 1o((¬ 𝑦 = 1o → ¬ 1o = 1o) → (1o = 1o → 𝑦 = 1o)) → EXMID)
27	16, 26	syl 14	. 2 ⊢ (∀𝑥 ∈ 𝒫 1o∀𝑦 ∈ 𝒫 1o((¬ 𝑦 = 1o → ¬ 𝑥 = 1o) → (𝑥 = 1o → 𝑦 = 1o)) → EXMID)
28	5, 27	impbii 126	1 ⊢ (EXMID ↔ ∀𝑥 ∈ 𝒫 1o∀𝑦 ∈ 𝒫 1o((¬ 𝑦 = 1o → ¬ 𝑥 = 1o) → (𝑥 = 1o → 𝑦 = 1o)))

Syntax hints:  ¬ wn 3   → wi 4   ∧ wa 104   ↔ wb 105  DECID wdc 846   = wceq 1402   ∈ wcel 2209  ∀wral 2528  𝒫 cpw 3688  EXMIDwem 4329  1_oc1o 6674

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 623  ax-in2 624  ax-io 721  ax-5 1500  ax-7 1501  ax-gen 1502  ax-ie1 1546  ax-ie2 1547  ax-8 1557  ax-10 1558  ax-11 1559  ax-i12 1560  ax-bndl 1562  ax-4 1563  ax-17 1579  ax-i9 1583  ax-ial 1587  ax-i5r 1588  ax-14 2212  ax-ext 2220  ax-sep 4247  ax-nul 4257  ax-pow 4309  ax-pr 4344  ax-un 4576

This theorem depends on definitions:  df-bi 117  df-stab 843  df-dc 847  df-tru 1405  df-fal 1408  df-nf 1514  df-sb 1816  df-clab 2225  df-cleq 2231  df-clel 2234  df-nfc 2381  df-ne 2421  df-ral 2533  df-rex 2534  df-rab 2537  df-v 2823  df-dif 3222  df-un 3224  df-in 3226  df-ss 3233  df-nul 3521  df-pw 3690  df-sn 3714  df-pr 3715  df-uni 3934  df-tr 4228  df-exmid 4330  df-iord 4509  df-on 4511  df-suc 4514  df-1o 6681

This theorem is referenced by: (None)