"Not too busy to not" or "not too busy not to"

Question

I'm not too busy to eat dinner

or

I'm not too busy not to eat dinner

Typically, you would need a double negative ("I'm not busy enough to not realized I skipped dinner," in that you weren't sufficiently busy to not know you skipped dinner; or "I'm not so sad to not go out to see my friends"), right?

Would negation + "too" + adjective require a double negative because if you negate one part, you would you need to negate the second part? Or would it be wrong to have the double negative? Is it wrong in general!?!

I'm too busy to eat dinner (i.e. due to a lack of time, I cannot eat dinner)

Would the opposite be: I'm not too busy to eat dinner -or- I'm not too busy to not eat dinner

Answer 1

As a general rule, double-negatives are almost always a no-no in English. There are some idiomatic cases where people will use them casually, but they are almost never grammatically correct.

If you want to negate a positive sentence which has multiple verbs (because it has sub-clauses), you generally only need/want to negate the main verb of the sentence. Subordinate verbs do not change, therefore the negative of:

I am too busy to eat dinner.

becomes

I am not too busy to eat dinner.

In the above, "to eat dinner" is modifying "busy", so the whole thing becomes a single entity in the larger sentence. Essentially, the thing that you're saying you are or are not is "too busy to eat dinner" (the whole phrase as one adjective). The nature of the thing you're talking about doesn't change depending on whether you are or are not actually that thing.