Set is Small Class
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Theorem
Let $x$ be a set.
Then $x$ is a small class.
Proof
- $x = x$
Therefore by Existential Generalisation:
- $\exists y: x = y$
$\blacksquare$
Add the appropriate words to link the above statements to the fact being proved, e.g. "Therefore by definition of ..." etc.
You can help $\mathsf{Pr} \infty \mathsf{fWiki}$ by explaining it. To discuss this point in more detail, feel free to use the talk page.
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Sources
- 1971: Gaisi Takeuti and Wilson M. Zaring: Introduction to Axiomatic Set Theory: $\S 4.11$
