Description: The set of positive integers exists. (Contributed by NM, 3-Oct-1999) (Revised by Mario Carneiro, 17-Nov-2014)
Ref | Expression | ||
---|---|---|---|
Assertion | nnex | $${\u22a2}\mathbb{N}\in \mathrm{V}$$ |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | cnex | $${\u22a2}\u2102\in \mathrm{V}$$ | |
2 | nnsscn | $${\u22a2}\mathbb{N}\subseteq \u2102$$ | |
3 | 1 2 | ssexi | $${\u22a2}\mathbb{N}\in \mathrm{V}$$ |