Uses of the past simple – traditional list
1. Single action in the past: Emma woke up at 6.30.
2. Continuous or repeated actions in the past: I played football twice a week when I was at school.
3. State in the past: Peter was ill for the last ten years of his life.
4. Polite conversation marker (present or future): Excuse me. I wondered if you had a few minutes after the meeting...
5. Present regret: I wish I had a job that paid more.
6. Counterfactual present: The children would understand if they were older.
7. Hypothetical future (viewed as not very probable: If I didn't get my degree next year, my father would be very disappointed.
As with the unmarked tense, it is true that the uses of the marked/stancing can be described in such ways as those noted, but such descriptions are not very helpful for the learner. In fact, there is an underlining simplicity to the system. The only 'rule' for the marked/distancing tense, traditionally known as the past simple is:
We use the marked form when we wish to distance the situation - in vividness, reality or directness.
Distancing in vividness
It is perfectly normal for a speaker to describe a past situation using the unmarked form (see Present Simple):
8. Then this chap just walks up to me and punches me.
The fact that the speaker has chosen not to distance the situation (which speaker and listener know from the context is distanced in time) makes the situation real, vivid.
However, if we simply wish to present the facts of the action, distanced in vividness/time, then we say:
8a. Then this chap just walked up to me and punched me.
In historic narrative and magazine articles the speaker/writer similarly chooses not to distance the situation. It is presented as something real and vivid, brought closer to us by the lack of distancing:
9. 3rd September 1939. 11 o'clock. Millions of people all over Britain gather anxiously round their radio sets. The strained voice of the Prime Minister comes across the air: "I have to tell you ...."
10. The Chancellor smiles almost ruefully as I pose the question. “Policies are more important than people," he begins, but we both know that voters disagree .
It is not the tense of the verb that shows us the time but such factors as explicit time markers  or the shared knowledge that the situation described occurred in the past . We can, if we wish, distance the situations:
9a. On 3rd September 1939 at 11 o'clock millions of people all over Britain gathered anxiously round...
10a.The Chancellor smiled almost ruefully as I posed the question.
What is past, even a few moments ago, is often viewed as past, finished, done with. It is therefore common for speakers/writers to use the marked (distancing) form of the verb to describe past situations, but it is not essential, as we have seen. The speaker/writer has the free choice: to distance or not to distance. Without explicit or implicit context, the use of the marked tense does not of itself imply past time; and describing past time does not necessarily involve the use of the unmarked tense.
Distancing in reality
Consider these two utterances:
11. Well, he has been in his new job a month now. I hope he likes it .
12. Well, he has been in his new job a month now. I wish he liked it .
In both, the underlined verb refers to the present or general (i.e. not specifically future or past) time. In  the hope and in , the wish are presented as facts. However, in  the liking is presented as a real possibility; in  the liking is presented as unreal; the speaker regrets that this is not the situation. The Unmarked form shows a distancing in perception of reality.
The idea of distancing in reality explains the use of tenses in the so-called First and Second Conditions:
13. George wants to see me tomorrow. If he offers me a rise I'll stay .
14. George wants to see me tomorrow. If he offered me a rise I'd stay.
In both utterances the time of the situation referred to is clearly future: tomorrow. In , the speaker has chosen not to distance the tense. The use of the unmarked form presents the situation as a real possibility. In , the speaker's use of the marked form distances the situation from reality: the prospect of the offer and the staying is less real.
When the context shows that the time of the situation is not future but present or general, then the reality of the situation is complete: we have hypothetical reality [= unreality], as in
15. I'd be in Africa now if the children weren't so settled here.
The speaker is not in Africa, and the children are settled here. The use of the distancing Marked form makes this clear. Any attempt to describe this as a special use of a so-called Past Tense is confusing; it has nothing to do with the past.
There is rarely any doubt about the time; if the context does not make it clear, then the speaker will make the time explicit. In an utterance such as
16. If they were here we could sort out any difficulties.
the time may be clear to speaker and listener. If it is not, the speaker will add a time marker such as now, tomorrow, next Tuesday , etc.
Distancing in directness
Some English coursebooks state that the use of could and would in requests is 'more polite' than can and will, as in:
17. Can/could you open the window please?
18. Will/would you post this letter when you go out?
If by 'more polite' we understand 'more diffident, more hesitant, less direct', then this is true. The reason, however, is not simply that some words are more polite than others. It is that could and would are the marked forms of can and will ; marked forms distance. Here the distancing is in directness. We see exactly the same use of marked forms for distancing in:
19. What was your name?
20. A: Did you want something? B: I wondered if you had a moment. I wanted to ask you about the meeting.
It is clear from these examples that the use of the marked tense does not in itself imply reference to past time. As noted near the beginning of this section:
We use the marked form when we wish to distance the situation in vividness, reality or directness .