Step
*
1
of Lemma
sq_stable__from_stable
1. [P] : ℙ
2. P supposing ¬¬P
3. ↓P
⊢ P
BY
{ BackThruHyp 2 }
1
1. P : ℙ
2. P supposing ¬¬P
3. ↓P
⊢ ¬¬P
Latex:
Latex:
1. [P] : \mBbbP{}
2. P supposing \mneg{}\mneg{}P
3. \mdownarrow{}P
\mvdash{} P
By
Latex:
BackThruHyp 2
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