Theorem varprop 38833

Description: Variables encoded as natural numbers are sentences of propositional calculus. (Contributed by Thomas van Maaren, 21-Aug-2026.)

Assertion

Ref	Expression
varprop	⊢ (𝑛 ∈ ℕ → (propvar ‘𝑛) ∈ PROP)

Proof of Theorem varprop

Dummy variables 𝑤 𝑥 𝑦 𝑧 are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		df-prop 38831	. . 3 ⊢ PROP = setrecs((𝑦 ∈ V ↦ {𝑥 ∣ (∃𝑧 ∈ 𝑦 (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ 𝑦 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))}))
2		0ex 5264	. . . 4 ⊢ ∅ ∈ V
3	2	a1i 11	. . 3 ⊢ (𝑛 ∈ ℕ → ∅ ∈ V)
4		0ss 4353	. . . 4 ⊢ ∅ ⊆ PROP
5	4	a1i 11	. . 3 ⊢ (𝑛 ∈ ℕ → ∅ ⊆ PROP)
6	1, 3, 5	setrec1 9996	. 2 ⊢ (𝑛 ∈ ℕ → ((𝑦 ∈ V ↦ {𝑥 ∣ (∃𝑧 ∈ 𝑦 (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ 𝑦 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))})‘∅) ⊆ PROP)
7		rspe 3256	. . . . . . 7 ⊢ ((𝑛 ∈ ℕ ∧ 𝑥 = (propvar ‘𝑛)) → ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))
8	7	olcd 888	. . . . . 6 ⊢ ((𝑛 ∈ ℕ ∧ 𝑥 = (propvar ‘𝑛)) → (∃𝑧 ∈ ∅ (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ ∅ 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛)))
9	8	ex 418	. . . . 5 ⊢ (𝑛 ∈ ℕ → (𝑥 = (propvar ‘𝑛) → (∃𝑧 ∈ ∅ (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ ∅ 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))))
10	9	alrimiv 1962	. . . 4 ⊢ (𝑛 ∈ ℕ → ∀𝑥(𝑥 = (propvar ‘𝑛) → (∃𝑧 ∈ ∅ (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ ∅ 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))))
11		fvex 6918	. . . . 5 ⊢ (propvar ‘𝑛) ∈ V
12		elab6g 3626	. . . . 5 ⊢ ((propvar ‘𝑛) ∈ V → ((propvar ‘𝑛) ∈ {𝑥 ∣ (∃𝑧 ∈ ∅ (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ ∅ 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))} ↔ ∀𝑥(𝑥 = (propvar ‘𝑛) → (∃𝑧 ∈ ∅ (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ ∅ 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛)))))
13	11, 12	ax-mp 5	. . . 4 ⊢ ((propvar ‘𝑛) ∈ {𝑥 ∣ (∃𝑧 ∈ ∅ (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ ∅ 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))} ↔ ∀𝑥(𝑥 = (propvar ‘𝑛) → (∃𝑧 ∈ ∅ (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ ∅ 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))))
14	10, 13	sylibr 237	. . 3 ⊢ (𝑛 ∈ ℕ → (propvar ‘𝑛) ∈ {𝑥 ∣ (∃𝑧 ∈ ∅ (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ ∅ 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))})
15		rexeq 3319	. . . . . . . . 9 ⊢ (𝑦 = ∅ → (∃𝑤 ∈ 𝑦 𝑥 = (𝑤prop→𝑧) ↔ ∃𝑤 ∈ ∅ 𝑥 = (𝑤prop→𝑧)))
16	15	orbi2d 929	. . . . . . . 8 ⊢ (𝑦 = ∅ → ((𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ 𝑦 𝑥 = (𝑤prop→𝑧)) ↔ (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ ∅ 𝑥 = (𝑤prop→𝑧))))
17	16	rexeqbi1dv 3334	. . . . . . 7 ⊢ (𝑦 = ∅ → (∃𝑧 ∈ 𝑦 (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ 𝑦 𝑥 = (𝑤prop→𝑧)) ↔ ∃𝑧 ∈ ∅ (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ ∅ 𝑥 = (𝑤prop→𝑧))))
18	17	orbi1d 930	. . . . . 6 ⊢ (𝑦 = ∅ → ((∃𝑧 ∈ 𝑦 (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ 𝑦 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛)) ↔ (∃𝑧 ∈ ∅ (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ ∅ 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))))
19	18	abbidv 2829	. . . . 5 ⊢ (𝑦 = ∅ → {𝑥 ∣ (∃𝑧 ∈ 𝑦 (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ 𝑦 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))} = {𝑥 ∣ (∃𝑧 ∈ ∅ (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ ∅ 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))})
20		eqid 2763	. . . . 5 ⊢ (𝑦 ∈ V ↦ {𝑥 ∣ (∃𝑧 ∈ 𝑦 (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ 𝑦 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))}) = (𝑦 ∈ V ↦ {𝑥 ∣ (∃𝑧 ∈ 𝑦 (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ 𝑦 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))})
21	2	dfproplem 38832	. . . . 5 ⊢ {𝑥 ∣ (∃𝑧 ∈ ∅ (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ ∅ 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))} ∈ V
22	19, 20, 21	fvmpt 7013	. . . 4 ⊢ (∅ ∈ V → ((𝑦 ∈ V ↦ {𝑥 ∣ (∃𝑧 ∈ 𝑦 (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ 𝑦 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))})‘∅) = {𝑥 ∣ (∃𝑧 ∈ ∅ (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ ∅ 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))})
23	2, 22	ax-mp 5	. . 3 ⊢ ((𝑦 ∈ V ↦ {𝑥 ∣ (∃𝑧 ∈ 𝑦 (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ 𝑦 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))})‘∅) = {𝑥 ∣ (∃𝑧 ∈ ∅ (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ ∅ 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))}
24	14, 23	eleqtrrdi 2875	. 2 ⊢ (𝑛 ∈ ℕ → (propvar ‘𝑛) ∈ ((𝑦 ∈ V ↦ {𝑥 ∣ (∃𝑧 ∈ 𝑦 (𝑥 = (prop¬‘𝑧) ∨ ∃𝑤 ∈ 𝑦 𝑥 = (𝑤prop→𝑧)) ∨ ∃𝑛 ∈ ℕ 𝑥 = (propvar ‘𝑛))})‘∅))
25	6, 24	sseldd 3914	1 ⊢ (𝑛 ∈ ℕ → (propvar ‘𝑛) ∈ PROP)

This proof depends on syntax axioms:   → wi 4   ↔ wb 209   ∧ wa 401   ∨ wo 861  ∀wal 1568   = wceq 1570   ∈ wcel 2147  {cab 2741  ∃wrex 3090  Vcvv 3454   ⊆ wss 3900  ∅c0 4281   ↦ cmpt 5189  ‘cfv 6555  (class class class)co 7440  ℕcn 12359  propvar cpropvar 38824  prop¬cpropneg 38825  prop→cpropimp 38826  PROPcprop 38830

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1828  ax-4 1842  ax-5 1945  ax-6 2002  ax-7 2043  ax-8 2149  ax-9 2157  ax-10 2180  ax-11 2197  ax-12 2216  ax-ext 2735  ax-rep 5235  ax-sep 5252  ax-nul 5263  ax-pow 5331  ax-pr 5395  ax-un 7772  ax-reg 9610  ax-inf2 9666  ax-cnex 11280  ax-1cn 11282  ax-addcl 11284

This proof depends on definitions:  df-bi 210  df-an 402  df-or 862  df-3or 1104  df-3an 1105  df-tru 1573  df-fal 1583  df-ex 1813  df-nf 1817  df-sb 2102  df-mo 2567  df-eu 2597  df-clab 2742  df-cleq 2755  df-clel 2839  df-nfc 2913  df-ne 2960  df-ral 3081  df-rex 3091  df-reu 3370  df-rab 3417  df-v 3456  df-sbc 3743  df-csb 3852  df-ss 3901  df-pss 4017  df-dif 4050  df-in 4094  df-un 4154  df-nul 4282  df-if 4486  df-pw 4562  df-sn 4589  df-pr 4591  df-op 4839  df-uni 4871  df-int 4911  df-iun 4956  df-iin 4957  df-br 5107  df-opab 5171  df-mpt 5190  df-tr 5216  df-id 5550  df-eprel 5555  df-po 5563  df-so 5564  df-fr 5608  df-we 5610  df-xp 5661  df-rel 5662  df-cnv 5663  df-co 5664  df-dm 5665  df-rn 5666  df-res 5667  df-ima 5668  df-pred 6319  df-ord 6380  df-on 6381  df-lim 6382  df-suc 6383  df-iota 6509  df-fun 6557  df-fn 6558  df-f 6559  df-f1 6560  df-fo 6561  df-f1o 6562  df-fv 6563  df-ov 7443  df-om 7899  df-2nd 8023  df-frecs 8324  df-wrecs 8355  df-recs 8404  df-rdg 8443  df-r1 9792  df-rank 9793  df-scott 9953  df-setrecs 9989  df-nn 12360  df-prop 38831

This theorem is used by:  dfprop1  38836