P. 105 of Theorem List - Metamath Proof Explorer

Theorem List for Metamath Proof Explorer - 10401-10500   *Has distinct variable group(s)

Type	Label	Description
Statement
Theorem	fin23lem13 10401*	Lemma for fin23 10458. Each step of 𝑈 is a decrease. (Contributed by Stefan O'Rear, 1-Nov-2014.)
⊢ 𝑈 = seqω((𝑖 ∈ ω, 𝑢 ∈ V ↦ if(((𝑡‘𝑖) ∩ 𝑢) = ∅, 𝑢, ((𝑡‘𝑖) ∩ 𝑢))), ∪ ran 𝑡)    ⇒   ⊢ (𝐴 ∈ ω → (𝑈‘suc 𝐴) ⊆ (𝑈‘𝐴))
Theorem	fin23lem14 10402*	Lemma for fin23 10458. 𝑈 will never evolve to an empty set if it did not start with one. (Contributed by Stefan O'Rear, 1-Nov-2014.)
⊢ 𝑈 = seqω((𝑖 ∈ ω, 𝑢 ∈ V ↦ if(((𝑡‘𝑖) ∩ 𝑢) = ∅, 𝑢, ((𝑡‘𝑖) ∩ 𝑢))), ∪ ran 𝑡)    ⇒   ⊢ ((𝐴 ∈ ω ∧ ∪ ran 𝑡 ≠ ∅) → (𝑈‘𝐴) ≠ ∅)
Theorem	fin23lem15 10403*	Lemma for fin23 10458. 𝑈 is a monotone function. (Contributed by Stefan O'Rear, 1-Nov-2014.)
⊢ 𝑈 = seqω((𝑖 ∈ ω, 𝑢 ∈ V ↦ if(((𝑡‘𝑖) ∩ 𝑢) = ∅, 𝑢, ((𝑡‘𝑖) ∩ 𝑢))), ∪ ran 𝑡)    ⇒   ⊢ (((𝐴 ∈ ω ∧ 𝐵 ∈ ω) ∧ 𝐵 ⊆ 𝐴) → (𝑈‘𝐴) ⊆ (𝑈‘𝐵))
Theorem	fin23lem16 10404*	Lemma for fin23 10458. 𝑈 ranges over the original set; in particular ran 𝑈 is a set, although we do not assume here that 𝑈 is. (Contributed by Stefan O'Rear, 1-Nov-2014.)
⊢ 𝑈 = seqω((𝑖 ∈ ω, 𝑢 ∈ V ↦ if(((𝑡‘𝑖) ∩ 𝑢) = ∅, 𝑢, ((𝑡‘𝑖) ∩ 𝑢))), ∪ ran 𝑡)    ⇒   ⊢ ∪ ran 𝑈 = ∪ ran 𝑡
Theorem	fin23lem19 10405*	Lemma for fin23 10458. The first set in 𝑈 to see an input set is either contained in it or disjoint from it. (Contributed by Stefan O'Rear, 1-Nov-2014.)
⊢ 𝑈 = seqω((𝑖 ∈ ω, 𝑢 ∈ V ↦ if(((𝑡‘𝑖) ∩ 𝑢) = ∅, 𝑢, ((𝑡‘𝑖) ∩ 𝑢))), ∪ ran 𝑡)    ⇒   ⊢ (𝐴 ∈ ω → ((𝑈‘suc 𝐴) ⊆ (𝑡‘𝐴) ∨ ((𝑈‘suc 𝐴) ∩ (𝑡‘𝐴)) = ∅))
Theorem	fin23lem20 10406*	Lemma for fin23 10458. 𝑋 is either contained in or disjoint from all input sets. (Contributed by Stefan O'Rear, 1-Nov-2014.)
⊢ 𝑈 = seqω((𝑖 ∈ ω, 𝑢 ∈ V ↦ if(((𝑡‘𝑖) ∩ 𝑢) = ∅, 𝑢, ((𝑡‘𝑖) ∩ 𝑢))), ∪ ran 𝑡)    ⇒   ⊢ (𝐴 ∈ ω → (∩ ran 𝑈 ⊆ (𝑡‘𝐴) ∨ (∩ ran 𝑈 ∩ (𝑡‘𝐴)) = ∅))
Theorem	fin23lem17 10407*	Lemma for fin23 10458. By ? Fin3DS ? , 𝑈 achieves its minimum (𝑋 in the synopsis above, but we will not be assigning a symbol here). TODO: Fix comment; math symbol Fin3DS does not exist. (Contributed by Stefan O'Rear, 4-Nov-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ 𝑈 = seqω((𝑖 ∈ ω, 𝑢 ∈ V ↦ if(((𝑡‘𝑖) ∩ 𝑢) = ∅, 𝑢, ((𝑡‘𝑖) ∩ 𝑢))), ∪ ran 𝑡)    &   ⊢ 𝐹 = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}    ⇒   ⊢ ((∪ ran 𝑡 ∈ 𝐹 ∧ 𝑡:ω–1-1→𝑉) → ∩ ran 𝑈 ∈ ran 𝑈)
Theorem	fin23lem21 10408*	Lemma for fin23 10458. 𝑋 is not empty. We only need here that 𝑡 has at least one set in its range besides ∅; the much stronger hypothesis here will serve as our induction hypothesis though. (Contributed by Stefan O'Rear, 1-Nov-2014.) (Revised by Mario Carneiro, 6-May-2015.)
⊢ 𝑈 = seqω((𝑖 ∈ ω, 𝑢 ∈ V ↦ if(((𝑡‘𝑖) ∩ 𝑢) = ∅, 𝑢, ((𝑡‘𝑖) ∩ 𝑢))), ∪ ran 𝑡)    &   ⊢ 𝐹 = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}    ⇒   ⊢ ((∪ ran 𝑡 ∈ 𝐹 ∧ 𝑡:ω–1-1→𝑉) → ∩ ran 𝑈 ≠ ∅)
Theorem	fin23lem28 10409*	Lemma for fin23 10458. The residual is also one-to-one. This preserves the induction invariant. (Contributed by Stefan O'Rear, 2-Nov-2014.)
⊢ 𝑈 = seqω((𝑖 ∈ ω, 𝑢 ∈ V ↦ if(((𝑡‘𝑖) ∩ 𝑢) = ∅, 𝑢, ((𝑡‘𝑖) ∩ 𝑢))), ∪ ran 𝑡)    &   ⊢ 𝐹 = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}    &   ⊢ 𝑃 = {𝑣 ∈ ω ∣ ∩ ran 𝑈 ⊆ (𝑡‘𝑣)}    &   ⊢ 𝑄 = (𝑤 ∈ ω ↦ (℩𝑥 ∈ 𝑃 (𝑥 ∩ 𝑃) ≈ 𝑤))    &   ⊢ 𝑅 = (𝑤 ∈ ω ↦ (℩𝑥 ∈ (ω ∖ 𝑃)(𝑥 ∩ (ω ∖ 𝑃)) ≈ 𝑤))    &   ⊢ 𝑍 = if(𝑃 ∈ Fin, (𝑡 ∘ 𝑅), ((𝑧 ∈ 𝑃 ↦ ((𝑡‘𝑧) ∖ ∩ ran 𝑈)) ∘ 𝑄))    ⇒   ⊢ (𝑡:ω–1-1→V → 𝑍:ω–1-1→V)
Theorem	fin23lem29 10410*	Lemma for fin23 10458. The residual is built from the same elements as the previous sequence. (Contributed by Stefan O'Rear, 2-Nov-2014.)
⊢ 𝑈 = seqω((𝑖 ∈ ω, 𝑢 ∈ V ↦ if(((𝑡‘𝑖) ∩ 𝑢) = ∅, 𝑢, ((𝑡‘𝑖) ∩ 𝑢))), ∪ ran 𝑡)    &   ⊢ 𝐹 = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}    &   ⊢ 𝑃 = {𝑣 ∈ ω ∣ ∩ ran 𝑈 ⊆ (𝑡‘𝑣)}    &   ⊢ 𝑄 = (𝑤 ∈ ω ↦ (℩𝑥 ∈ 𝑃 (𝑥 ∩ 𝑃) ≈ 𝑤))    &   ⊢ 𝑅 = (𝑤 ∈ ω ↦ (℩𝑥 ∈ (ω ∖ 𝑃)(𝑥 ∩ (ω ∖ 𝑃)) ≈ 𝑤))    &   ⊢ 𝑍 = if(𝑃 ∈ Fin, (𝑡 ∘ 𝑅), ((𝑧 ∈ 𝑃 ↦ ((𝑡‘𝑧) ∖ ∩ ran 𝑈)) ∘ 𝑄))    ⇒   ⊢ ∪ ran 𝑍 ⊆ ∪ ran 𝑡
Theorem	fin23lem30 10411*	Lemma for fin23 10458. The residual is disjoint from the common set. (Contributed by Stefan O'Rear, 2-Nov-2014.)
⊢ 𝑈 = seqω((𝑖 ∈ ω, 𝑢 ∈ V ↦ if(((𝑡‘𝑖) ∩ 𝑢) = ∅, 𝑢, ((𝑡‘𝑖) ∩ 𝑢))), ∪ ran 𝑡)    &   ⊢ 𝐹 = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}    &   ⊢ 𝑃 = {𝑣 ∈ ω ∣ ∩ ran 𝑈 ⊆ (𝑡‘𝑣)}    &   ⊢ 𝑄 = (𝑤 ∈ ω ↦ (℩𝑥 ∈ 𝑃 (𝑥 ∩ 𝑃) ≈ 𝑤))    &   ⊢ 𝑅 = (𝑤 ∈ ω ↦ (℩𝑥 ∈ (ω ∖ 𝑃)(𝑥 ∩ (ω ∖ 𝑃)) ≈ 𝑤))    &   ⊢ 𝑍 = if(𝑃 ∈ Fin, (𝑡 ∘ 𝑅), ((𝑧 ∈ 𝑃 ↦ ((𝑡‘𝑧) ∖ ∩ ran 𝑈)) ∘ 𝑄))    ⇒   ⊢ (Fun 𝑡 → (∪ ran 𝑍 ∩ ∩ ran 𝑈) = ∅)
Theorem	fin23lem31 10412*	Lemma for fin23 10458. The residual is has a strictly smaller range than the previous sequence. This will be iterated to build an unbounded chain. (Contributed by Stefan O'Rear, 2-Nov-2014.)
⊢ 𝑈 = seqω((𝑖 ∈ ω, 𝑢 ∈ V ↦ if(((𝑡‘𝑖) ∩ 𝑢) = ∅, 𝑢, ((𝑡‘𝑖) ∩ 𝑢))), ∪ ran 𝑡)    &   ⊢ 𝐹 = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}    &   ⊢ 𝑃 = {𝑣 ∈ ω ∣ ∩ ran 𝑈 ⊆ (𝑡‘𝑣)}    &   ⊢ 𝑄 = (𝑤 ∈ ω ↦ (℩𝑥 ∈ 𝑃 (𝑥 ∩ 𝑃) ≈ 𝑤))    &   ⊢ 𝑅 = (𝑤 ∈ ω ↦ (℩𝑥 ∈ (ω ∖ 𝑃)(𝑥 ∩ (ω ∖ 𝑃)) ≈ 𝑤))    &   ⊢ 𝑍 = if(𝑃 ∈ Fin, (𝑡 ∘ 𝑅), ((𝑧 ∈ 𝑃 ↦ ((𝑡‘𝑧) ∖ ∩ ran 𝑈)) ∘ 𝑄))    ⇒   ⊢ ((𝑡:ω–1-1→𝑉 ∧ 𝐺 ∈ 𝐹 ∧ ∪ ran 𝑡 ⊆ 𝐺) → ∪ ran 𝑍 ⊊ ∪ ran 𝑡)
Theorem	fin23lem32 10413*	Lemma for fin23 10458. Wrap the previous construction into a function to hide the hypotheses. (Contributed by Stefan O'Rear, 2-Nov-2014.)
⊢ 𝑈 = seqω((𝑖 ∈ ω, 𝑢 ∈ V ↦ if(((𝑡‘𝑖) ∩ 𝑢) = ∅, 𝑢, ((𝑡‘𝑖) ∩ 𝑢))), ∪ ran 𝑡)    &   ⊢ 𝐹 = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}    &   ⊢ 𝑃 = {𝑣 ∈ ω ∣ ∩ ran 𝑈 ⊆ (𝑡‘𝑣)}    &   ⊢ 𝑄 = (𝑤 ∈ ω ↦ (℩𝑥 ∈ 𝑃 (𝑥 ∩ 𝑃) ≈ 𝑤))    &   ⊢ 𝑅 = (𝑤 ∈ ω ↦ (℩𝑥 ∈ (ω ∖ 𝑃)(𝑥 ∩ (ω ∖ 𝑃)) ≈ 𝑤))    &   ⊢ 𝑍 = if(𝑃 ∈ Fin, (𝑡 ∘ 𝑅), ((𝑧 ∈ 𝑃 ↦ ((𝑡‘𝑧) ∖ ∩ ran 𝑈)) ∘ 𝑄))    ⇒   ⊢ (𝐺 ∈ 𝐹 → ∃𝑓∀𝑏((𝑏:ω–1-1→V ∧ ∪ ran 𝑏 ⊆ 𝐺) → ((𝑓‘𝑏):ω–1-1→V ∧ ∪ ran (𝑓‘𝑏) ⊊ ∪ ran 𝑏)))
Theorem	fin23lem33 10414*	Lemma for fin23 10458. Discharge hypotheses. (Contributed by Stefan O'Rear, 2-Nov-2014.)
⊢ 𝐹 = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}    ⇒   ⊢ (𝐺 ∈ 𝐹 → ∃𝑓∀𝑏((𝑏:ω–1-1→V ∧ ∪ ran 𝑏 ⊆ 𝐺) → ((𝑓‘𝑏):ω–1-1→V ∧ ∪ ran (𝑓‘𝑏) ⊊ ∪ ran 𝑏)))
Theorem	fin23lem34 10415*	Lemma for fin23 10458. Establish induction invariants on 𝑌 which parameterizes our contradictory chain of subsets. In this section, ℎ is the hypothetically assumed family of subsets, 𝑔 is the ground set, and 𝑖 is the induction function constructed in the previous section. (Contributed by Stefan O'Rear, 2-Nov-2014.)
⊢ 𝐹 = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}    &   ⊢ (𝜑 → ℎ:ω–1-1→V)    &   ⊢ (𝜑 → ∪ ran ℎ ⊆ 𝐺)    &   ⊢ (𝜑 → ∀𝑗((𝑗:ω–1-1→V ∧ ∪ ran 𝑗 ⊆ 𝐺) → ((𝑖‘𝑗):ω–1-1→V ∧ ∪ ran (𝑖‘𝑗) ⊊ ∪ ran 𝑗)))    &   ⊢ 𝑌 = (rec(𝑖, ℎ) ↾ ω)    ⇒   ⊢ ((𝜑 ∧ 𝐴 ∈ ω) → ((𝑌‘𝐴):ω–1-1→V ∧ ∪ ran (𝑌‘𝐴) ⊆ 𝐺))
Theorem	fin23lem35 10416*	Lemma for fin23 10458. Strict order property of 𝑌. (Contributed by Stefan O'Rear, 2-Nov-2014.)
⊢ 𝐹 = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}    &   ⊢ (𝜑 → ℎ:ω–1-1→V)    &   ⊢ (𝜑 → ∪ ran ℎ ⊆ 𝐺)    &   ⊢ (𝜑 → ∀𝑗((𝑗:ω–1-1→V ∧ ∪ ran 𝑗 ⊆ 𝐺) → ((𝑖‘𝑗):ω–1-1→V ∧ ∪ ran (𝑖‘𝑗) ⊊ ∪ ran 𝑗)))    &   ⊢ 𝑌 = (rec(𝑖, ℎ) ↾ ω)    ⇒   ⊢ ((𝜑 ∧ 𝐴 ∈ ω) → ∪ ran (𝑌‘suc 𝐴) ⊊ ∪ ran (𝑌‘𝐴))
Theorem	fin23lem36 10417*	Lemma for fin23 10458. Weak order property of 𝑌. (Contributed by Stefan O'Rear, 2-Nov-2014.)
⊢ 𝐹 = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}    &   ⊢ (𝜑 → ℎ:ω–1-1→V)    &   ⊢ (𝜑 → ∪ ran ℎ ⊆ 𝐺)    &   ⊢ (𝜑 → ∀𝑗((𝑗:ω–1-1→V ∧ ∪ ran 𝑗 ⊆ 𝐺) → ((𝑖‘𝑗):ω–1-1→V ∧ ∪ ran (𝑖‘𝑗) ⊊ ∪ ran 𝑗)))    &   ⊢ 𝑌 = (rec(𝑖, ℎ) ↾ ω)    ⇒   ⊢ (((𝐴 ∈ ω ∧ 𝐵 ∈ ω) ∧ (𝐵 ⊆ 𝐴 ∧ 𝜑)) → ∪ ran (𝑌‘𝐴) ⊆ ∪ ran (𝑌‘𝐵))
Theorem	fin23lem38 10418*	Lemma for fin23 10458. The contradictory chain has no minimum. (Contributed by Stefan O'Rear, 2-Nov-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ 𝐹 = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}    &   ⊢ (𝜑 → ℎ:ω–1-1→V)    &   ⊢ (𝜑 → ∪ ran ℎ ⊆ 𝐺)    &   ⊢ (𝜑 → ∀𝑗((𝑗:ω–1-1→V ∧ ∪ ran 𝑗 ⊆ 𝐺) → ((𝑖‘𝑗):ω–1-1→V ∧ ∪ ran (𝑖‘𝑗) ⊊ ∪ ran 𝑗)))    &   ⊢ 𝑌 = (rec(𝑖, ℎ) ↾ ω)    ⇒   ⊢ (𝜑 → ¬ ∩ ran (𝑏 ∈ ω ↦ ∪ ran (𝑌‘𝑏)) ∈ ran (𝑏 ∈ ω ↦ ∪ ran (𝑌‘𝑏)))
Theorem	fin23lem39 10419*	Lemma for fin23 10458. Thus, we have that 𝑔 could not have been in 𝐹 after all. (Contributed by Stefan O'Rear, 4-Nov-2014.)
⊢ 𝐹 = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}    &   ⊢ (𝜑 → ℎ:ω–1-1→V)    &   ⊢ (𝜑 → ∪ ran ℎ ⊆ 𝐺)    &   ⊢ (𝜑 → ∀𝑗((𝑗:ω–1-1→V ∧ ∪ ran 𝑗 ⊆ 𝐺) → ((𝑖‘𝑗):ω–1-1→V ∧ ∪ ran (𝑖‘𝑗) ⊊ ∪ ran 𝑗)))    &   ⊢ 𝑌 = (rec(𝑖, ℎ) ↾ ω)    ⇒   ⊢ (𝜑 → ¬ 𝐺 ∈ 𝐹)
Theorem	fin23lem40 10420*	Lemma for fin23 10458. FinII sets satisfy the descending chain condition. (Contributed by Stefan O'Rear, 3-Nov-2014.)
⊢ 𝐹 = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}    ⇒   ⊢ (𝐴 ∈ FinII → 𝐴 ∈ 𝐹)
Theorem	fin23lem41 10421*	Lemma for fin23 10458. A set which satisfies the descending sequence condition must be III-finite. (Contributed by Stefan O'Rear, 2-Nov-2014.)
⊢ 𝐹 = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}    ⇒   ⊢ (𝐴 ∈ 𝐹 → 𝐴 ∈ FinIII)
Theorem	isf32lem1 10422*	Lemma for isfin3-2 10436. Derive weak ordering property. (Contributed by Stefan O'Rear, 5-Nov-2014.)
⊢ (𝜑 → 𝐹:ω⟶𝒫 𝐺)    &   ⊢ (𝜑 → ∀𝑥 ∈ ω (𝐹‘suc 𝑥) ⊆ (𝐹‘𝑥))    &   ⊢ (𝜑 → ¬ ∩ ran 𝐹 ∈ ran 𝐹)    ⇒   ⊢ (((𝐴 ∈ ω ∧ 𝐵 ∈ ω) ∧ (𝐵 ⊆ 𝐴 ∧ 𝜑)) → (𝐹‘𝐴) ⊆ (𝐹‘𝐵))
Theorem	isf32lem2 10423*	Lemma for isfin3-2 10436. Non-minimum implies that there is always another decrease. (Contributed by Stefan O'Rear, 5-Nov-2014.)
⊢ (𝜑 → 𝐹:ω⟶𝒫 𝐺)    &   ⊢ (𝜑 → ∀𝑥 ∈ ω (𝐹‘suc 𝑥) ⊆ (𝐹‘𝑥))    &   ⊢ (𝜑 → ¬ ∩ ran 𝐹 ∈ ran 𝐹)    ⇒   ⊢ ((𝜑 ∧ 𝐴 ∈ ω) → ∃𝑎 ∈ ω (𝐴 ∈ 𝑎 ∧ (𝐹‘suc 𝑎) ⊊ (𝐹‘𝑎)))
Theorem	isf32lem3 10424*	Lemma for isfin3-2 10436. Being a chain, difference sets are disjoint (one case). (Contributed by Stefan O'Rear, 5-Nov-2014.)
⊢ (𝜑 → 𝐹:ω⟶𝒫 𝐺)    &   ⊢ (𝜑 → ∀𝑥 ∈ ω (𝐹‘suc 𝑥) ⊆ (𝐹‘𝑥))    &   ⊢ (𝜑 → ¬ ∩ ran 𝐹 ∈ ran 𝐹)    ⇒   ⊢ (((𝐴 ∈ ω ∧ 𝐵 ∈ ω) ∧ (𝐵 ∈ 𝐴 ∧ 𝜑)) → (((𝐹‘𝐴) ∖ (𝐹‘suc 𝐴)) ∩ ((𝐹‘𝐵) ∖ (𝐹‘suc 𝐵))) = ∅)
Theorem	isf32lem4 10425*	Lemma for isfin3-2 10436. Being a chain, difference sets are disjoint. (Contributed by Stefan O'Rear, 5-Nov-2014.)
⊢ (𝜑 → 𝐹:ω⟶𝒫 𝐺)    &   ⊢ (𝜑 → ∀𝑥 ∈ ω (𝐹‘suc 𝑥) ⊆ (𝐹‘𝑥))    &   ⊢ (𝜑 → ¬ ∩ ran 𝐹 ∈ ran 𝐹)    ⇒   ⊢ (((𝜑 ∧ 𝐴 ≠ 𝐵) ∧ (𝐴 ∈ ω ∧ 𝐵 ∈ ω)) → (((𝐹‘𝐴) ∖ (𝐹‘suc 𝐴)) ∩ ((𝐹‘𝐵) ∖ (𝐹‘suc 𝐵))) = ∅)
Theorem	isf32lem5 10426*	Lemma for isfin3-2 10436. There are infinite decrease points. (Contributed by Stefan O'Rear, 5-Nov-2014.)
⊢ (𝜑 → 𝐹:ω⟶𝒫 𝐺)    &   ⊢ (𝜑 → ∀𝑥 ∈ ω (𝐹‘suc 𝑥) ⊆ (𝐹‘𝑥))    &   ⊢ (𝜑 → ¬ ∩ ran 𝐹 ∈ ran 𝐹)    &   ⊢ 𝑆 = {𝑦 ∈ ω ∣ (𝐹‘suc 𝑦) ⊊ (𝐹‘𝑦)}    ⇒   ⊢ (𝜑 → ¬ 𝑆 ∈ Fin)
Theorem	isf32lem6 10427*	Lemma for isfin3-2 10436. Each K value is nonempty. (Contributed by Stefan O'Rear, 5-Nov-2014.)
⊢ (𝜑 → 𝐹:ω⟶𝒫 𝐺)    &   ⊢ (𝜑 → ∀𝑥 ∈ ω (𝐹‘suc 𝑥) ⊆ (𝐹‘𝑥))    &   ⊢ (𝜑 → ¬ ∩ ran 𝐹 ∈ ran 𝐹)    &   ⊢ 𝑆 = {𝑦 ∈ ω ∣ (𝐹‘suc 𝑦) ⊊ (𝐹‘𝑦)}    &   ⊢ 𝐽 = (𝑢 ∈ ω ↦ (℩𝑣 ∈ 𝑆 (𝑣 ∩ 𝑆) ≈ 𝑢))    &   ⊢ 𝐾 = ((𝑤 ∈ 𝑆 ↦ ((𝐹‘𝑤) ∖ (𝐹‘suc 𝑤))) ∘ 𝐽)    ⇒   ⊢ ((𝜑 ∧ 𝐴 ∈ ω) → (𝐾‘𝐴) ≠ ∅)
Theorem	isf32lem7 10428*	Lemma for isfin3-2 10436. Different K values are disjoint. (Contributed by Stefan O'Rear, 5-Nov-2014.)
⊢ (𝜑 → 𝐹:ω⟶𝒫 𝐺)    &   ⊢ (𝜑 → ∀𝑥 ∈ ω (𝐹‘suc 𝑥) ⊆ (𝐹‘𝑥))    &   ⊢ (𝜑 → ¬ ∩ ran 𝐹 ∈ ran 𝐹)    &   ⊢ 𝑆 = {𝑦 ∈ ω ∣ (𝐹‘suc 𝑦) ⊊ (𝐹‘𝑦)}    &   ⊢ 𝐽 = (𝑢 ∈ ω ↦ (℩𝑣 ∈ 𝑆 (𝑣 ∩ 𝑆) ≈ 𝑢))    &   ⊢ 𝐾 = ((𝑤 ∈ 𝑆 ↦ ((𝐹‘𝑤) ∖ (𝐹‘suc 𝑤))) ∘ 𝐽)    ⇒   ⊢ (((𝜑 ∧ 𝐴 ≠ 𝐵) ∧ (𝐴 ∈ ω ∧ 𝐵 ∈ ω)) → ((𝐾‘𝐴) ∩ (𝐾‘𝐵)) = ∅)
Theorem	isf32lem8 10429*	Lemma for isfin3-2 10436. K sets are subsets of the base. (Contributed by Stefan O'Rear, 6-Nov-2014.)
⊢ (𝜑 → 𝐹:ω⟶𝒫 𝐺)    &   ⊢ (𝜑 → ∀𝑥 ∈ ω (𝐹‘suc 𝑥) ⊆ (𝐹‘𝑥))    &   ⊢ (𝜑 → ¬ ∩ ran 𝐹 ∈ ran 𝐹)    &   ⊢ 𝑆 = {𝑦 ∈ ω ∣ (𝐹‘suc 𝑦) ⊊ (𝐹‘𝑦)}    &   ⊢ 𝐽 = (𝑢 ∈ ω ↦ (℩𝑣 ∈ 𝑆 (𝑣 ∩ 𝑆) ≈ 𝑢))    &   ⊢ 𝐾 = ((𝑤 ∈ 𝑆 ↦ ((𝐹‘𝑤) ∖ (𝐹‘suc 𝑤))) ∘ 𝐽)    ⇒   ⊢ ((𝜑 ∧ 𝐴 ∈ ω) → (𝐾‘𝐴) ⊆ 𝐺)
Theorem	isf32lem9 10430*	Lemma for isfin3-2 10436. Construction of the onto function. (Contributed by Stefan O'Rear, 5-Nov-2014.) (Revised by Mario Carneiro, 2-Oct-2015.)
⊢ (𝜑 → 𝐹:ω⟶𝒫 𝐺)    &   ⊢ (𝜑 → ∀𝑥 ∈ ω (𝐹‘suc 𝑥) ⊆ (𝐹‘𝑥))    &   ⊢ (𝜑 → ¬ ∩ ran 𝐹 ∈ ran 𝐹)    &   ⊢ 𝑆 = {𝑦 ∈ ω ∣ (𝐹‘suc 𝑦) ⊊ (𝐹‘𝑦)}    &   ⊢ 𝐽 = (𝑢 ∈ ω ↦ (℩𝑣 ∈ 𝑆 (𝑣 ∩ 𝑆) ≈ 𝑢))    &   ⊢ 𝐾 = ((𝑤 ∈ 𝑆 ↦ ((𝐹‘𝑤) ∖ (𝐹‘suc 𝑤))) ∘ 𝐽)    &   ⊢ 𝐿 = (𝑡 ∈ 𝐺 ↦ (℩𝑠(𝑠 ∈ ω ∧ 𝑡 ∈ (𝐾‘𝑠))))    ⇒   ⊢ (𝜑 → 𝐿:𝐺–onto→ω)
Theorem	isf32lem10 10431*	Lemma for isfin3-2 . Write in terms of weak dominance. (Contributed by Stefan O'Rear, 6-Nov-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ (𝜑 → 𝐹:ω⟶𝒫 𝐺)    &   ⊢ (𝜑 → ∀𝑥 ∈ ω (𝐹‘suc 𝑥) ⊆ (𝐹‘𝑥))    &   ⊢ (𝜑 → ¬ ∩ ran 𝐹 ∈ ran 𝐹)    &   ⊢ 𝑆 = {𝑦 ∈ ω ∣ (𝐹‘suc 𝑦) ⊊ (𝐹‘𝑦)}    &   ⊢ 𝐽 = (𝑢 ∈ ω ↦ (℩𝑣 ∈ 𝑆 (𝑣 ∩ 𝑆) ≈ 𝑢))    &   ⊢ 𝐾 = ((𝑤 ∈ 𝑆 ↦ ((𝐹‘𝑤) ∖ (𝐹‘suc 𝑤))) ∘ 𝐽)    &   ⊢ 𝐿 = (𝑡 ∈ 𝐺 ↦ (℩𝑠(𝑠 ∈ ω ∧ 𝑡 ∈ (𝐾‘𝑠))))    ⇒   ⊢ (𝜑 → (𝐺 ∈ 𝑉 → ω ≼* 𝐺))
Theorem	isf32lem11 10432*	Lemma for isfin3-2 10436. Remove hypotheses from isf32lem10 10431. (Contributed by Stefan O'Rear, 17-May-2015.)
⊢ ((𝐺 ∈ 𝑉 ∧ (𝐹:ω⟶𝒫 𝐺 ∧ ∀𝑏 ∈ ω (𝐹‘suc 𝑏) ⊆ (𝐹‘𝑏) ∧ ¬ ∩ ran 𝐹 ∈ ran 𝐹)) → ω ≼* 𝐺)
Theorem	isf32lem12 10433*	Lemma for isfin3-2 10436. (Contributed by Stefan O'Rear, 6-Nov-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ 𝐹 = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}    ⇒   ⊢ (𝐺 ∈ 𝑉 → (¬ ω ≼* 𝐺 → 𝐺 ∈ 𝐹))
Theorem	isfin32i 10434	One half of isfin3-2 10436. (Contributed by Mario Carneiro, 3-Jun-2015.)
⊢ (𝐴 ∈ FinIII → ¬ ω ≼* 𝐴)
Theorem	isf33lem 10435*	Lemma for isfin3-3 10437. (Contributed by Stefan O'Rear, 17-May-2015.)
⊢ FinIII = {𝑔 ∣ ∀𝑎 ∈ (𝒫 𝑔 ↑m ω)(∀𝑥 ∈ ω (𝑎‘suc 𝑥) ⊆ (𝑎‘𝑥) → ∩ ran 𝑎 ∈ ran 𝑎)}
Theorem	isfin3-2 10436	Weakly Dedekind-infinite sets are exactly those which can be mapped onto ω. (Contributed by Stefan O'Rear, 6-Nov-2014.) (Proof shortened by Mario Carneiro, 17-May-2015.)
⊢ (𝐴 ∈ 𝑉 → (𝐴 ∈ FinIII ↔ ¬ ω ≼* 𝐴))
Theorem	isfin3-3 10437*	Weakly Dedekind-infinite sets are exactly those with an ω-indexed descending chain of subsets. (Contributed by Stefan O'Rear, 7-Nov-2014.)
⊢ (𝐴 ∈ 𝑉 → (𝐴 ∈ FinIII ↔ ∀𝑓 ∈ (𝒫 𝐴 ↑m ω)(∀𝑥 ∈ ω (𝑓‘suc 𝑥) ⊆ (𝑓‘𝑥) → ∩ ran 𝑓 ∈ ran 𝑓)))
Theorem	fin33i 10438*	Inference from isfin3-3 10437. (This is actually a bit stronger than isfin3-3 10437 because it does not assume 𝐹 is a set and does not use the Axiom of Infinity either.) (Contributed by Mario Carneiro, 17-May-2015.)
⊢ ((𝐴 ∈ FinIII ∧ 𝐹:ω⟶𝒫 𝐴 ∧ ∀𝑥 ∈ ω (𝐹‘suc 𝑥) ⊆ (𝐹‘𝑥)) → ∩ ran 𝐹 ∈ ran 𝐹)
Theorem	compsscnvlem 10439*	Lemma for compsscnv 10440. (Contributed by Mario Carneiro, 17-May-2015.)
⊢ ((𝑥 ∈ 𝒫 𝐴 ∧ 𝑦 = (𝐴 ∖ 𝑥)) → (𝑦 ∈ 𝒫 𝐴 ∧ 𝑥 = (𝐴 ∖ 𝑦)))
Theorem	compsscnv 10440*	Complementation on a power set lattice is an involution. (Contributed by Mario Carneiro, 17-May-2015.)
⊢ 𝐹 = (𝑥 ∈ 𝒫 𝐴 ↦ (𝐴 ∖ 𝑥))    ⇒   ⊢ ◡𝐹 = 𝐹
Theorem	isf34lem1 10441*	Lemma for isfin3-4 10451. (Contributed by Stefan O'Rear, 7-Nov-2014.)
⊢ 𝐹 = (𝑥 ∈ 𝒫 𝐴 ↦ (𝐴 ∖ 𝑥))    ⇒   ⊢ ((𝐴 ∈ 𝑉 ∧ 𝑋 ⊆ 𝐴) → (𝐹‘𝑋) = (𝐴 ∖ 𝑋))
Theorem	isf34lem2 10442*	Lemma for isfin3-4 10451. (Contributed by Stefan O'Rear, 7-Nov-2014.)
⊢ 𝐹 = (𝑥 ∈ 𝒫 𝐴 ↦ (𝐴 ∖ 𝑥))    ⇒   ⊢ (𝐴 ∈ 𝑉 → 𝐹:𝒫 𝐴⟶𝒫 𝐴)
Theorem	compssiso 10443*	Complementation is an antiautomorphism on power set lattices. (Contributed by Stefan O'Rear, 4-Nov-2014.) (Proof shortened by Mario Carneiro, 17-May-2015.)
⊢ 𝐹 = (𝑥 ∈ 𝒫 𝐴 ↦ (𝐴 ∖ 𝑥))    ⇒   ⊢ (𝐴 ∈ 𝑉 → 𝐹 Isom [⊊] , ◡ [⊊] (𝒫 𝐴, 𝒫 𝐴))
Theorem	isf34lem3 10444*	Lemma for isfin3-4 10451. (Contributed by Stefan O'Rear, 7-Nov-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ 𝐹 = (𝑥 ∈ 𝒫 𝐴 ↦ (𝐴 ∖ 𝑥))    ⇒   ⊢ ((𝐴 ∈ 𝑉 ∧ 𝑋 ⊆ 𝒫 𝐴) → (𝐹 “ (𝐹 “ 𝑋)) = 𝑋)
Theorem	compss 10445*	Express image under of the complementation isomorphism. (Contributed by Stefan O'Rear, 5-Nov-2014.) (Proof shortened by Mario Carneiro, 17-May-2015.)
⊢ 𝐹 = (𝑥 ∈ 𝒫 𝐴 ↦ (𝐴 ∖ 𝑥))    ⇒   ⊢ (𝐹 “ 𝐺) = {𝑦 ∈ 𝒫 𝐴 ∣ (𝐴 ∖ 𝑦) ∈ 𝐺}
Theorem	isf34lem4 10446*	Lemma for isfin3-4 10451. (Contributed by Stefan O'Rear, 7-Nov-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ 𝐹 = (𝑥 ∈ 𝒫 𝐴 ↦ (𝐴 ∖ 𝑥))    ⇒   ⊢ ((𝐴 ∈ 𝑉 ∧ (𝑋 ⊆ 𝒫 𝐴 ∧ 𝑋 ≠ ∅)) → (𝐹‘∪ 𝑋) = ∩ (𝐹 “ 𝑋))
Theorem	isf34lem5 10447*	Lemma for isfin3-4 10451. (Contributed by Stefan O'Rear, 7-Nov-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ 𝐹 = (𝑥 ∈ 𝒫 𝐴 ↦ (𝐴 ∖ 𝑥))    ⇒   ⊢ ((𝐴 ∈ 𝑉 ∧ (𝑋 ⊆ 𝒫 𝐴 ∧ 𝑋 ≠ ∅)) → (𝐹‘∩ 𝑋) = ∪ (𝐹 “ 𝑋))
Theorem	isf34lem7 10448*	Lemma for isfin3-4 10451. (Contributed by Stefan O'Rear, 7-Nov-2014.)
⊢ 𝐹 = (𝑥 ∈ 𝒫 𝐴 ↦ (𝐴 ∖ 𝑥))    ⇒   ⊢ ((𝐴 ∈ FinIII ∧ 𝐺:ω⟶𝒫 𝐴 ∧ ∀𝑦 ∈ ω (𝐺‘𝑦) ⊆ (𝐺‘suc 𝑦)) → ∪ ran 𝐺 ∈ ran 𝐺)
Theorem	isf34lem6 10449*	Lemma for isfin3-4 10451. (Contributed by Stefan O'Rear, 7-Nov-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ 𝐹 = (𝑥 ∈ 𝒫 𝐴 ↦ (𝐴 ∖ 𝑥))    ⇒   ⊢ (𝐴 ∈ 𝑉 → (𝐴 ∈ FinIII ↔ ∀𝑓 ∈ (𝒫 𝐴 ↑m ω)(∀𝑦 ∈ ω (𝑓‘𝑦) ⊆ (𝑓‘suc 𝑦) → ∪ ran 𝑓 ∈ ran 𝑓)))
Theorem	fin34i 10450*	Inference from isfin3-4 10451. (Contributed by Mario Carneiro, 17-May-2015.)
⊢ ((𝐴 ∈ FinIII ∧ 𝐺:ω⟶𝒫 𝐴 ∧ ∀𝑥 ∈ ω (𝐺‘𝑥) ⊆ (𝐺‘suc 𝑥)) → ∪ ran 𝐺 ∈ ran 𝐺)
Theorem	isfin3-4 10451*	Weakly Dedekind-infinite sets are exactly those with an ω-indexed ascending chain of subsets. (Contributed by Stefan O'Rear, 7-Nov-2014.) (Proof shortened by Mario Carneiro, 17-May-2015.)
⊢ (𝐴 ∈ 𝑉 → (𝐴 ∈ FinIII ↔ ∀𝑓 ∈ (𝒫 𝐴 ↑m ω)(∀𝑥 ∈ ω (𝑓‘𝑥) ⊆ (𝑓‘suc 𝑥) → ∪ ran 𝑓 ∈ ran 𝑓)))
Theorem	fin11a 10452	Every I-finite set is Ia-finite. (Contributed by Stefan O'Rear, 30-Oct-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ (𝐴 ∈ Fin → 𝐴 ∈ FinIa)
Theorem	enfin1ai 10453	Ia-finiteness is a cardinal property. (Contributed by Mario Carneiro, 18-May-2015.)
⊢ (𝐴 ≈ 𝐵 → (𝐴 ∈ FinIa → 𝐵 ∈ FinIa))
Theorem	isfin1-2 10454	A set is finite in the usual sense iff the power set of its power set is Dedekind finite. (Contributed by Stefan O'Rear, 3-Nov-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ (𝐴 ∈ Fin ↔ 𝒫 𝒫 𝐴 ∈ FinIV)
Theorem	isfin1-3 10455	A set is I-finite iff every system of subsets contains a maximal subset. Definition I of [Levy58] p. 2. (Contributed by Stefan O'Rear, 4-Nov-2014.) (Proof shortened by Mario Carneiro, 17-May-2015.)
⊢ (𝐴 ∈ 𝑉 → (𝐴 ∈ Fin ↔ ◡ [⊊] Fr 𝒫 𝐴))
Theorem	isfin1-4 10456	A set is I-finite iff every system of subsets contains a minimal subset. (Contributed by Stefan O'Rear, 4-Nov-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ (𝐴 ∈ 𝑉 → (𝐴 ∈ Fin ↔ [⊊] Fr 𝒫 𝐴))
Theorem	dffin1-5 10457	Compact quantifier-free version of the standard definition df-fin 9007. (Contributed by Stefan O'Rear, 6-Jan-2015.)
⊢ Fin = ( ≈ “ ω)
Theorem	fin23 10458	Every II-finite set (every chain of subsets has a maximal element) is III-finite (has no denumerable collection of subsets). The proof here is the only one I could find, from http://matwbn.icm.edu.pl/ksiazki/fm/fm6/fm619.pdf p.94 (writeup by Tarski, credited to Kuratowski). Translated into English and modern notation, the proof proceeds as follows (variables renamed for uniqueness): Suppose for a contradiction that 𝐴 is a set which is II-finite but not III-finite. For any countable sequence of distinct subsets 𝑇 of 𝐴, we can form a decreasing sequence of nonempty subsets (𝑈‘𝑇) by taking finite intersections of initial segments of 𝑇 while skipping over any element of 𝑇 which would cause the intersection to be empty. By II-finiteness (as fin2i2 10387) this sequence contains its intersection, call it 𝑌; since by induction every subset in the sequence 𝑈 is nonempty, the intersection must be nonempty. Suppose that an element 𝑋 of 𝑇 has nonempty intersection with 𝑌. Thus, said element has a nonempty intersection with the corresponding element of 𝑈, therefore it was used in the construction of 𝑈 and all further elements of 𝑈 are subsets of 𝑋, thus 𝑋 contains the 𝑌. That is, all elements of 𝑋 either contain 𝑌 or are disjoint from it. Since there are only two cases, there must exist an infinite subset of 𝑇 which uniformly either contain 𝑌 or are disjoint from it. In the former case we can create an infinite set by subtracting 𝑌 from each element. In either case, call the result 𝑍; this is an infinite set of subsets of 𝐴, each of which is disjoint from 𝑌 and contained in the union of 𝑇; the union of 𝑍 is strictly contained in the union of 𝑇, because only the latter is a superset of the nonempty set 𝑌. The preceding four steps may be iterated a countable number of times starting from the assumed denumerable set of subsets to produce a denumerable sequence 𝐵 of the 𝑇 sets from each stage. Great caution is required to avoid ax-dc 10515 here; in particular an effective version of the pigeonhole principle (for aleph-null pigeons and 2 holes) is required. Since a denumerable set of subsets is assumed to exist, we can conclude ω ∈ V without the axiom. This 𝐵 sequence is strictly decreasing, thus it has no minimum, contradicting the first assumption. (Contributed by Stefan O'Rear, 2-Nov-2014.) (Proof shortened by Mario Carneiro, 17-May-2015.)
⊢ (𝐴 ∈ FinII → 𝐴 ∈ FinIII)
Theorem	fin34 10459	Every III-finite set is IV-finite. (Contributed by Stefan O'Rear, 30-Oct-2014.)
⊢ (𝐴 ∈ FinIII → 𝐴 ∈ FinIV)
Theorem	isfin5-2 10460	Alternate definition of V-finite which emphasizes the idempotent behavior of V-infinite sets. (Contributed by Stefan O'Rear, 30-Oct-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ (𝐴 ∈ 𝑉 → (𝐴 ∈ FinV ↔ ¬ (𝐴 ≠ ∅ ∧ 𝐴 ≈ (𝐴 ⊔ 𝐴))))
Theorem	fin45 10461	Every IV-finite set is V-finite: if we can pack two copies of the set into itself, we can certainly leave space. (Contributed by Stefan O'Rear, 30-Oct-2014.) (Proof shortened by Mario Carneiro, 18-May-2015.)
⊢ (𝐴 ∈ FinIV → 𝐴 ∈ FinV)
Theorem	fin56 10462	Every V-finite set is VI-finite because multiplication dominates addition for cardinals. (Contributed by Stefan O'Rear, 29-Oct-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ (𝐴 ∈ FinV → 𝐴 ∈ FinVI)
Theorem	fin17 10463	Every I-finite set is VII-finite. (Contributed by Mario Carneiro, 17-May-2015.)
⊢ (𝐴 ∈ Fin → 𝐴 ∈ FinVII)
Theorem	fin67 10464	Every VI-finite set is VII-finite. (Contributed by Stefan O'Rear, 29-Oct-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ (𝐴 ∈ FinVI → 𝐴 ∈ FinVII)
Theorem	isfin7-2 10465	A set is VII-finite iff it is non-well-orderable or finite. (Contributed by Mario Carneiro, 17-May-2015.)
⊢ (𝐴 ∈ 𝑉 → (𝐴 ∈ FinVII ↔ (𝐴 ∈ dom card → 𝐴 ∈ Fin)))
Theorem	fin71num 10466	A well-orderable set is VII-finite iff it is I-finite. Thus, even without choice, on the class of well-orderable sets all eight definitions of finite set coincide. (Contributed by Mario Carneiro, 18-May-2015.)
⊢ (𝐴 ∈ dom card → (𝐴 ∈ FinVII ↔ 𝐴 ∈ Fin))
Theorem	dffin7-2 10467	Class form of isfin7-2 10465. (Contributed by Mario Carneiro, 17-May-2015.)
⊢ FinVII = (Fin ∪ (V ∖ dom card))
Theorem	dfacfin7 10468	Axiom of Choice equivalent: the VII-finite sets are the same as I-finite sets. (Contributed by Mario Carneiro, 18-May-2015.)
⊢ (CHOICE ↔ FinVII = Fin)
Theorem	fin1a2lem1 10469	Lemma for fin1a2 10484. (Contributed by Stefan O'Rear, 7-Nov-2014.)
⊢ 𝑆 = (𝑥 ∈ On ↦ suc 𝑥)    ⇒   ⊢ (𝐴 ∈ On → (𝑆‘𝐴) = suc 𝐴)
Theorem	fin1a2lem2 10470	Lemma for fin1a2 10484. The successor operation on the ordinal numbers is injective or one-to-one. Lemma 1.17 of [Schloeder] p. 2. (Contributed by Stefan O'Rear, 7-Nov-2014.)
⊢ 𝑆 = (𝑥 ∈ On ↦ suc 𝑥)    ⇒   ⊢ 𝑆:On–1-1→On
Theorem	fin1a2lem3 10471	Lemma for fin1a2 10484. (Contributed by Stefan O'Rear, 7-Nov-2014.)
⊢ 𝐸 = (𝑥 ∈ ω ↦ (2o ·o 𝑥))    ⇒   ⊢ (𝐴 ∈ ω → (𝐸‘𝐴) = (2o ·o 𝐴))
Theorem	fin1a2lem4 10472	Lemma for fin1a2 10484. (Contributed by Stefan O'Rear, 7-Nov-2014.)
⊢ 𝐸 = (𝑥 ∈ ω ↦ (2o ·o 𝑥))    ⇒   ⊢ 𝐸:ω–1-1→ω
Theorem	fin1a2lem5 10473	Lemma for fin1a2 10484. (Contributed by Stefan O'Rear, 7-Nov-2014.)
⊢ 𝐸 = (𝑥 ∈ ω ↦ (2o ·o 𝑥))    ⇒   ⊢ (𝐴 ∈ ω → (𝐴 ∈ ran 𝐸 ↔ ¬ suc 𝐴 ∈ ran 𝐸))
Theorem	fin1a2lem6 10474	Lemma for fin1a2 10484. Establish that ω can be broken into two equipollent pieces. (Contributed by Stefan O'Rear, 7-Nov-2014.)
⊢ 𝐸 = (𝑥 ∈ ω ↦ (2o ·o 𝑥))    &   ⊢ 𝑆 = (𝑥 ∈ On ↦ suc 𝑥)    ⇒   ⊢ (𝑆 ↾ ran 𝐸):ran 𝐸–1-1-onto→(ω ∖ ran 𝐸)
Theorem	fin1a2lem7 10475*	Lemma for fin1a2 10484. Split a III-infinite set in two pieces. (Contributed by Stefan O'Rear, 7-Nov-2014.)
⊢ 𝐸 = (𝑥 ∈ ω ↦ (2o ·o 𝑥))    &   ⊢ 𝑆 = (𝑥 ∈ On ↦ suc 𝑥)    ⇒   ⊢ ((𝐴 ∈ 𝑉 ∧ ∀𝑦 ∈ 𝒫 𝐴(𝑦 ∈ FinIII ∨ (𝐴 ∖ 𝑦) ∈ FinIII)) → 𝐴 ∈ FinIII)
Theorem	fin1a2lem8 10476*	Lemma for fin1a2 10484. Split a III-infinite set in two pieces. (Contributed by Stefan O'Rear, 7-Nov-2014.)
⊢ ((𝐴 ∈ 𝑉 ∧ ∀𝑥 ∈ 𝒫 𝐴(𝑥 ∈ FinIII ∨ (𝐴 ∖ 𝑥) ∈ FinIII)) → 𝐴 ∈ FinIII)
Theorem	fin1a2lem9 10477*	Lemma for fin1a2 10484. In a chain of finite sets, initial segments are finite. (Contributed by Stefan O'Rear, 8-Nov-2014.)
⊢ (( [⊊] Or 𝑋 ∧ 𝑋 ⊆ Fin ∧ 𝐴 ∈ ω) → {𝑏 ∈ 𝑋 ∣ 𝑏 ≼ 𝐴} ∈ Fin)
Theorem	fin1a2lem10 10478	Lemma for fin1a2 10484. A nonempty finite union of members of a chain is a member of the chain. (Contributed by Stefan O'Rear, 8-Nov-2014.)
⊢ ((𝐴 ≠ ∅ ∧ 𝐴 ∈ Fin ∧ [⊊] Or 𝐴) → ∪ 𝐴 ∈ 𝐴)
Theorem	fin1a2lem11 10479*	Lemma for fin1a2 10484. (Contributed by Stefan O'Rear, 8-Nov-2014.)
⊢ (( [⊊] Or 𝐴 ∧ 𝐴 ⊆ Fin) → ran (𝑏 ∈ ω ↦ ∪ {𝑐 ∈ 𝐴 ∣ 𝑐 ≼ 𝑏}) = (𝐴 ∪ {∅}))
Theorem	fin1a2lem12 10480	Lemma for fin1a2 10484. (Contributed by Stefan O'Rear, 8-Nov-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ (((𝐴 ⊆ 𝒫 𝐵 ∧ [⊊] Or 𝐴 ∧ ¬ ∪ 𝐴 ∈ 𝐴) ∧ (𝐴 ⊆ Fin ∧ 𝐴 ≠ ∅)) → ¬ 𝐵 ∈ FinIII)
Theorem	fin1a2lem13 10481	Lemma for fin1a2 10484. (Contributed by Stefan O'Rear, 8-Nov-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ (((𝐴 ⊆ 𝒫 𝐵 ∧ [⊊] Or 𝐴 ∧ ¬ ∪ 𝐴 ∈ 𝐴) ∧ (¬ 𝐶 ∈ Fin ∧ 𝐶 ∈ 𝐴)) → ¬ (𝐵 ∖ 𝐶) ∈ FinII)
Theorem	fin12 10482	Weak theorem which skips Ia but has a trivial proof, needed to prove fin1a2 10484. (Contributed by Stefan O'Rear, 8-Nov-2014.) (Revised by Mario Carneiro, 17-May-2015.)
⊢ (𝐴 ∈ Fin → 𝐴 ∈ FinII)
Theorem	fin1a2s 10483*	An II-infinite set can have an I-infinite part broken off and remain II-infinite. (Contributed by Stefan O'Rear, 8-Nov-2014.) (Proof shortened by Mario Carneiro, 17-May-2015.)
⊢ ((𝐴 ∈ 𝑉 ∧ ∀𝑥 ∈ 𝒫 𝐴(𝑥 ∈ Fin ∨ (𝐴 ∖ 𝑥) ∈ FinII)) → 𝐴 ∈ FinII)
Theorem	fin1a2 10484	Every Ia-finite set is II-finite. Theorem 1 of [Levy58], p. 3. (Contributed by Stefan O'Rear, 8-Nov-2014.) (Proof shortened by Mario Carneiro, 17-May-2015.)
⊢ (𝐴 ∈ FinIa → 𝐴 ∈ FinII)
2.6.17  Hereditarily size-limited sets without Choice
Theorem	itunifval 10485*	Function value of iterated unions. EDITORIAL: The iterated unions and order types of ordered sets are split out here because they could conceivably be independently useful. (Contributed by Stefan O'Rear, 11-Feb-2015.)
⊢ 𝑈 = (𝑥 ∈ V ↦ (rec((𝑦 ∈ V ↦ ∪ 𝑦), 𝑥) ↾ ω))    ⇒   ⊢ (𝐴 ∈ 𝑉 → (𝑈‘𝐴) = (rec((𝑦 ∈ V ↦ ∪ 𝑦), 𝐴) ↾ ω))
Theorem	itunifn 10486*	Functionality of the iterated union. (Contributed by Stefan O'Rear, 11-Feb-2015.)
⊢ 𝑈 = (𝑥 ∈ V ↦ (rec((𝑦 ∈ V ↦ ∪ 𝑦), 𝑥) ↾ ω))    ⇒   ⊢ (𝐴 ∈ 𝑉 → (𝑈‘𝐴) Fn ω)
Theorem	ituni0 10487*	A zero-fold iterated union. (Contributed by Stefan O'Rear, 11-Feb-2015.)
⊢ 𝑈 = (𝑥 ∈ V ↦ (rec((𝑦 ∈ V ↦ ∪ 𝑦), 𝑥) ↾ ω))    ⇒   ⊢ (𝐴 ∈ 𝑉 → ((𝑈‘𝐴)‘∅) = 𝐴)
Theorem	itunisuc 10488*	Successor iterated union. (Contributed by Stefan O'Rear, 11-Feb-2015.)
⊢ 𝑈 = (𝑥 ∈ V ↦ (rec((𝑦 ∈ V ↦ ∪ 𝑦), 𝑥) ↾ ω))    ⇒   ⊢ ((𝑈‘𝐴)‘suc 𝐵) = ∪ ((𝑈‘𝐴)‘𝐵)
Theorem	itunitc1 10489*	Each union iterate is a member of the transitive closure. (Contributed by Stefan O'Rear, 11-Feb-2015.)
⊢ 𝑈 = (𝑥 ∈ V ↦ (rec((𝑦 ∈ V ↦ ∪ 𝑦), 𝑥) ↾ ω))    ⇒   ⊢ ((𝑈‘𝐴)‘𝐵) ⊆ (TC‘𝐴)
Theorem	itunitc 10490*	The union of all union iterates creates the transitive closure; compare trcl 9797. (Contributed by Stefan O'Rear, 11-Feb-2015.)
⊢ 𝑈 = (𝑥 ∈ V ↦ (rec((𝑦 ∈ V ↦ ∪ 𝑦), 𝑥) ↾ ω))    ⇒   ⊢ (TC‘𝐴) = ∪ ran (𝑈‘𝐴)
Theorem	ituniiun 10491*	Unwrap an iterated union from the "other end". (Contributed by Stefan O'Rear, 11-Feb-2015.)
⊢ 𝑈 = (𝑥 ∈ V ↦ (rec((𝑦 ∈ V ↦ ∪ 𝑦), 𝑥) ↾ ω))    ⇒   ⊢ (𝐴 ∈ 𝑉 → ((𝑈‘𝐴)‘suc 𝐵) = ∪ 𝑎 ∈ 𝐴 ((𝑈‘𝑎)‘𝐵))
Theorem	hsmexlem7 10492*	Lemma for hsmex 10501. Properties of the recurrent sequence of ordinals. (Contributed by Stefan O'Rear, 14-Feb-2015.)
⊢ 𝐻 = (rec((𝑧 ∈ V ↦ (har‘𝒫 (𝑋 × 𝑧))), (har‘𝒫 𝑋)) ↾ ω)    ⇒   ⊢ (𝐻‘∅) = (har‘𝒫 𝑋)
Theorem	hsmexlem8 10493*	Lemma for hsmex 10501. Properties of the recurrent sequence of ordinals. (Contributed by Stefan O'Rear, 14-Feb-2015.)
⊢ 𝐻 = (rec((𝑧 ∈ V ↦ (har‘𝒫 (𝑋 × 𝑧))), (har‘𝒫 𝑋)) ↾ ω)    ⇒   ⊢ (𝑎 ∈ ω → (𝐻‘suc 𝑎) = (har‘𝒫 (𝑋 × (𝐻‘𝑎))))
Theorem	hsmexlem9 10494*	Lemma for hsmex 10501. Properties of the recurrent sequence of ordinals. (Contributed by Stefan O'Rear, 14-Feb-2015.)
⊢ 𝐻 = (rec((𝑧 ∈ V ↦ (har‘𝒫 (𝑋 × 𝑧))), (har‘𝒫 𝑋)) ↾ ω)    ⇒   ⊢ (𝑎 ∈ ω → (𝐻‘𝑎) ∈ On)
Theorem	hsmexlem1 10495	Lemma for hsmex 10501. Bound the order type of a limited-cardinality set of ordinals. (Contributed by Stefan O'Rear, 14-Feb-2015.) (Revised by Mario Carneiro, 26-Jun-2015.)
⊢ 𝑂 = OrdIso( E , 𝐴)    ⇒   ⊢ ((𝐴 ⊆ On ∧ 𝐴 ≼* 𝐵) → dom 𝑂 ∈ (har‘𝒫 𝐵))
Theorem	hsmexlem2 10496*	Lemma for hsmex 10501. Bound the order type of a union of sets of ordinals, each of limited order type. Vaguely reminiscent of unictb 10644 but use of order types allows to canonically choose the sub-bijections, removing the choice requirement. (Contributed by Stefan O'Rear, 14-Feb-2015.) (Revised by Mario Carneiro, 26-Jun-2015.) (Revised by AV, 18-Sep-2021.)
⊢ 𝐹 = OrdIso( E , 𝐵)    &   ⊢ 𝐺 = OrdIso( E , ∪ 𝑎 ∈ 𝐴 𝐵)    ⇒   ⊢ ((𝐴 ∈ 𝑉 ∧ 𝐶 ∈ On ∧ ∀𝑎 ∈ 𝐴 (𝐵 ∈ 𝒫 On ∧ dom 𝐹 ∈ 𝐶)) → dom 𝐺 ∈ (har‘𝒫 (𝐴 × 𝐶)))
Theorem	hsmexlem3 10497*	Lemma for hsmex 10501. Clear 𝐼 hypothesis and extend previous result by dominance. Note that this could be substantially strengthened, e.g., using the weak Hartogs function, but all we need here is that there be *some* dominating ordinal. (Contributed by Stefan O'Rear, 14-Feb-2015.) (Revised by Mario Carneiro, 26-Jun-2015.)
⊢ 𝐹 = OrdIso( E , 𝐵)    &   ⊢ 𝐺 = OrdIso( E , ∪ 𝑎 ∈ 𝐴 𝐵)    ⇒   ⊢ (((𝐴 ≼* 𝐷 ∧ 𝐶 ∈ On) ∧ ∀𝑎 ∈ 𝐴 (𝐵 ∈ 𝒫 On ∧ dom 𝐹 ∈ 𝐶)) → dom 𝐺 ∈ (har‘𝒫 (𝐷 × 𝐶)))
Theorem	hsmexlem4 10498*	Lemma for hsmex 10501. The core induction, establishing bounds on the order types of iterated unions of the initial set. (Contributed by Stefan O'Rear, 14-Feb-2015.)
⊢ 𝑋 ∈ V    &   ⊢ 𝐻 = (rec((𝑧 ∈ V ↦ (har‘𝒫 (𝑋 × 𝑧))), (har‘𝒫 𝑋)) ↾ ω)    &   ⊢ 𝑈 = (𝑥 ∈ V ↦ (rec((𝑦 ∈ V ↦ ∪ 𝑦), 𝑥) ↾ ω))    &   ⊢ 𝑆 = {𝑎 ∈ ∪ (𝑅1 “ On) ∣ ∀𝑏 ∈ (TC‘{𝑎})𝑏 ≼ 𝑋}    &   ⊢ 𝑂 = OrdIso( E , (rank “ ((𝑈‘𝑑)‘𝑐)))    ⇒   ⊢ ((𝑐 ∈ ω ∧ 𝑑 ∈ 𝑆) → dom 𝑂 ∈ (𝐻‘𝑐))
Theorem	hsmexlem5 10499*	Lemma for hsmex 10501. Combining the above constraints, along with itunitc 10490 and tcrank 9953, gives an effective constraint on the rank of 𝑆. (Contributed by Stefan O'Rear, 14-Feb-2015.)
⊢ 𝑋 ∈ V    &   ⊢ 𝐻 = (rec((𝑧 ∈ V ↦ (har‘𝒫 (𝑋 × 𝑧))), (har‘𝒫 𝑋)) ↾ ω)    &   ⊢ 𝑈 = (𝑥 ∈ V ↦ (rec((𝑦 ∈ V ↦ ∪ 𝑦), 𝑥) ↾ ω))    &   ⊢ 𝑆 = {𝑎 ∈ ∪ (𝑅1 “ On) ∣ ∀𝑏 ∈ (TC‘{𝑎})𝑏 ≼ 𝑋}    &   ⊢ 𝑂 = OrdIso( E , (rank “ ((𝑈‘𝑑)‘𝑐)))    ⇒   ⊢ (𝑑 ∈ 𝑆 → (rank‘𝑑) ∈ (har‘𝒫 (ω × ∪ ran 𝐻)))
Theorem	hsmexlem6 10500*	Lemma for hsmex 10501. (Contributed by Stefan O'Rear, 14-Feb-2015.)
⊢ 𝑋 ∈ V    &   ⊢ 𝐻 = (rec((𝑧 ∈ V ↦ (har‘𝒫 (𝑋 × 𝑧))), (har‘𝒫 𝑋)) ↾ ω)    &   ⊢ 𝑈 = (𝑥 ∈ V ↦ (rec((𝑦 ∈ V ↦ ∪ 𝑦), 𝑥) ↾ ω))    &   ⊢ 𝑆 = {𝑎 ∈ ∪ (𝑅1 “ On) ∣ ∀𝑏 ∈ (TC‘{𝑎})𝑏 ≼ 𝑋}    &   ⊢ 𝑂 = OrdIso( E , (rank “ ((𝑈‘𝑑)‘𝑐)))    ⇒   ⊢ 𝑆 ∈ V