it/that, sooner/earlier

[Tapies]

Hi,

please could you explain to me the differences?

I didn't say it.
I didn't say that.
When to use it, when to use that - in general?

He came earlier.
He came sooner.

Thank you.
T.

[Soup]

I didn't say it.
I didn't say that.

In that context, it and that are synomyns and refer to the same thing:

Ex: I didn't say it--that the world was flat.
Ex: I didn't say that--that the world was flat.

One difference between it and that,is deixis:

Ex: I didn't say that (i.e., what you just said).
Cf. I didn't say it (i.e., what Max said that I said).

He came earlier than we expected.
He came sooner than we expected.

The difference, sooner is a type of deictic word (See deixis above):

Ex: We asked Max to come at 8 p.m., but he came earlier than we expected--at 7:30 p.m.

Ex: The doctor said the baby's head was about to crown, but that it would at least another hour before the baby was born; however, the baby came sooner than we expected--10 minutes later.