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Mirrors > Home > ILE Home > Th. List > a9e | GIF version |
Description: At least one individual exists. This is not a theorem of free logic, which is sound in empty domains. For such a logic, we would add this theorem as an axiom of set theory (Axiom 0 of [Kunen] p. 10). In the system consisting of ax-5 1381 through ax-14 1450 and ax-17 1464, all axioms other than ax-9 1469 are believed to be theorems of free logic, although the system without ax-9 1469 is probably not complete in free logic. (Contributed by NM, 5-Aug-1993.) (Revised by NM, 3-Feb-2015.) |
Ref | Expression |
---|---|
a9e | ⊢ ∃𝑥 𝑥 = 𝑦 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ax-i9 1468 | 1 ⊢ ∃𝑥 𝑥 = 𝑦 |
Colors of variables: wff set class |
Syntax hints: ∃wex 1426 |
This theorem was proved from axioms: ax-i9 1468 |
This theorem is referenced by: ax9o 1633 equid 1634 equs4 1660 equsal 1662 equsex 1663 equsexd 1664 spimt 1671 spimeh 1674 spimed 1675 equvini 1688 ax11v2 1748 ax11v 1755 ax11ev 1756 equs5or 1758 euequ1 2043 |
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