gerund or infinitive?

[navit]

Which are correct:

1) Stealing that money is something you shouldn't think about.
2) Stealing is something you shouldn't think about.

3) To steal that money is something you shouldn't think about.
4 To steal is something you shouldn't think about.


Gratefully,
Navi

[Alan]

#3 & 4, while theoretically possible, are highly unnatural.

An infinitive as subject is generally restricted to generalized/hypothetical contexts (particularly with forms of the conditional mood), e.g.

To steal that wallet would be a sin.


For a Viking, to die in battle was the greatest possible honour.


For most other purposes, a gerund will be the idiomatic choice.