What does "as you told me to" in negative sentence mean?

Question

a. I didn't close the door, as you told me to.

Does that mean:

1. You told me to close the door and I didn't.
2. You told me not to close the door and I didn't.

How about:

b. I didn't close the door, as you told me not to.

Does 'as' mean 'because' in (b)?

Answer 1

There are indeed two syntactic readings of this structure, which can be distinguished by phraseology (and helped by punctuation).

In the first, "as" means "like" or more specifically "according to the manner in which".

In the second, "as" means "because" or more specifically "in view of the fact that".

In your first example, it must be the first reading, since it wouldn't make sense to say you didn't close the door because they told you to.

So it means: You told me to close the door and I didn't.

However, it could also be the case that you were told the exact manner in which you should close the door. Then the sentence could mean: I closed the door, but not in the way you told me to. (We would write it without a comma in this case.)

In your second example, it must be the "because" reading, as you suggested. Otherwise the negatives pile up to absurdity.

Answer 2

Sentence a. is badly written because it's ambiguous. If someone said that to me, without any clarifying context (like, I either told them to close the door or told them not to close the door), I'd have to ask them what they meant.

To be clear on where the ambiguity lies, here's two parsings:

I [didn't close the door], as you told me to.
I didn't [close the door, as you told me to].

The first means I didn't close the door, which means I followed your instructions. The second means I didn't do what you told me to do, which was to close the door.

Sentence b. is unambiguous. It only means you told me not to close the door, and I did not close the door.