X Mode, if I might proffer a slightly different way of looking at this...

1.After I ate dinner, I stepped outside for some fresh air.

This Clause Complex consists of two clauses.

|| after I ate dinner............. ||....I stepped outside for some fresh air ||
DEPENDENT CLAUSE (FINITE)|| ......INDEPENDENT CLAUSE

The first is a Finite Dependent Clause. The Finite involved is "ate", which is a Tense (as opposed to a Modal) Finite. In this case both the Finite (Past Tense) and the Predicator (the referent action of the infinitive "to eat") are contained in one word.


2. After eating dinner, I stepped outside for some fresh air.

||| after eating dinner....... ||...I stepped outside for some fresh air |||
DEP. CLAUSE (NONFINITE) ||.......INDEPENDENT CLAUSE

This Clause Complex also contains two clauses. The first is - unlike the first clause of Number 1 above - a Nonfinite Clause (all Nonfinite Clauses are Dependent, ie they CANNOT stand alone as complete written sentences). There is no information contained in this clause with respect to Tense or Modality. The Clause Complex containing the Nonfinite Clause does not have restrictions imposed on it by that Nonfinite Clause with respect to Tense.

For example, after a clause such as

||After eating dinner|| (NONFINITE)

any of the following Finite Independent Clauses could follow to result in a grammatically correct Clause Complex:

...I stepped outside for some fresh air;
...I step outside for some fresh air;
...I had been stepping outside for some fresh air;
...I have been stepping outside for some fresh air;
...I will step outside for some fresh air;
...I must step outside;
...I needed to...
...I would have....

and so on and so forth - there are many possibilities,

whereas we do not have this range of options open to us after a Finite Dependent Clause:

|| After I ate dinner|| (FINITE)

...I stepped outside for some fresh air.
...I needed to step outside for some fresh air

and so on through a much more restricted range of possibilities. That is, the Finite (Past) Dependent Clause restricts the Independent Clause to the Past Tense, while the Nonfinite Clause has a much broader application.

I hope you can see something of the range of uses to which Nonfinite Clauses such as the above might be put.


By the way, Finite Clauses contain propositions that are said to be "arguable". For example -

A: ...after I ate dinner...
B: ...after what?....
A: ...I ate dinner...
B: ...no you didn't...
A: ...yes, I did....
B: ...you didn't...
A: ..I did...
A: ..didnt...
B: ...did...

- here we can see that argument can be reduced to a simple exchange involving the polarity (positive or negative) of the Finite (in this case "did": did eat = ate ).

You can't do that with a Nonfinite Clause:

A: ...after eating dinner...
B:...after what?...
A ...eating dinner...
B:... yes... (thinks: damn, there's nothing there to disagree with!)

Good health.