When is the past perfect exactly needed?

Question

I have never had this problem before. But after seeing some questions posted on ELU, I started to doubt. I have been through links¹, pages of grammar books², a lot of questions³ posted here and ELU. I now still can't seem to understand how the past perfect is exactly used. The references sometimes even contradict each other.

What I had understood so far was

The past perfect is not necessary if we are not 'going back' to the earlier past, and simply moving from one event to another.

but I then saw a lot of other 'rules' including

If the sequence is clear, the past perfect is not needed.

which is slightly different, less 'narrow' and can be applied in more situations than the first rule^A, and

The past perfect is optional only when talking about an action at a specific time.

This is confusing. Can anyone here clarify things out please?

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^A For example, for

Doing the survey [completed] -> Showing the result

We showed the result of the survey we did.

If the second rule is applied, the sentence above is fine (the sequence is clear), but not if the first rule since we are not moving from any event to the next and possibly even going back.

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¹ English Pages and English Grammar Secrets

² Practical English Usage (2005) by Michael Swan, Collins Cobuild Student's Grammar (1991). Upper-Intermediate Cutting Edge.

³ including Is it possible to be grammatically correct without using past perfect?, When is using the past perfect tense not necessary?, Past vs Past Perfect, Past Perfect sentences with “before” etc.

Answer 1

The truth is that there are many situations and sentences which allow for either the past perfect tense or the past simple tense, with very little change to the sentence. The key difference between the past perfect and past simple tenses is the explicit order of two (or more) events in the past. There are of course many nuances in usage that make this a fairly complex topic, which I can only partly cover here. First, here is a brief overview of some of the relevant usages and rules of past simple and past perfect:

Past Simple

• A completed action or condition in the past.
• Must have a time reference, but this may be implied.
• May be used for a sequence of multiple events, but only for chronological order or explicit times.

The third point is where the past simple tense overlaps with the past perfect tense, and is what I will be focusing on.

Simple tenses are often represented as a single dot on a timeline, such as the one below. In the case of past simple, this represents that the event is completed entirely in the past. If past simple is used to list multiple events, then we represent it with multiple unconnected dots in the past, arranged in chronological order.

e.g. I ate breakfast this morning and then my brother arrived.

Past Perfect

Two (or more) completed linked actions or conditions in the past.

Tense is formed by linking a past perfect clause (first event) with a past simple clause (second event).

The two events have a specified order, so chronological order and explicit times are uncessary.

Perfect tenses are often represented by two dots with a connecting "bridge" on the timeline. This represents both the order (past perfect clause = left dot; past simple clause = right dot) and linking of the two events.

e.g. I had already eaten breakfast when my brother arrived.

Note: I find that timelines such as this often help my students understand tense usage better. This particular timeline is one I use often and is from this site.

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The past perfect is not necessary if we are not 'going back' to the earlier past, and simply moving from one event to another.

This is correct. Past simple can be used to list multiple events in the past, but they should always be in order of occurrence, from longest ago to most recent (or have some other way of explicitly stating the order of events).

Yesterday I went to work, and then did some shopping.

If we use the past perfect tense instead, then we have more flexibility in the sentence structure while still being grammatically correct.

I had gone to work yesterday before I did some shopping.

or

I did some shopping yesterday after I had gone to work.

You can see that when using the past perfect tense we can list events in whichever order we prefer, rather than being restricted to chronological order.

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If the sequence is clear, the past perfect is not needed.

Again, this is correct. However, there are nuances here. For the sequence to be "clear" you must either list events in chronological order as I mentioned before, or explicitly state the order or time in the sentence. This is often ignored by native speakers because the order of events can usually be inferred from the sentence without it being explicitly stated. In fact your example sentence shows this phenomena. I will again denote longest ago and most recent.

We showed the result of the survey we did.

We can in this case correctly infer that the survey was completed before the results were shown, it is simple logic. However, if you wish to be more clear (and grammatically correct) then it is better to write it in the past perfect tense.

We showed the result of the survey we had done.

I recommend my students to always use explicit ordering of events for the sake of clarity, so that the reader/listener does not need to use logic to deduce the order. Most prefer to do this by using the past perfect tense, or chronological order of events in the past simple tense.

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The past perfect is optional [i.e. may be replaced by past simple] only when talking about an action at a specific time.

This "rule" is a combination of the usage rules for past simple and past perfect. As I mentioned before, one of the rules of past simple is that it must include a time, which can be either implied or specified. However, when the past simple is used to replace the past perfect, more information (i.e. a specific time) is needed to provide the same information to the reader/listener that the past perfect tense would have given.

Answer 2

I recommend keeping three basic uses of the Present Perfect in mind:

1. Life Experience
2. Change in Situation (in which the change is relevant to the present)
3. Up to Now

Examples:

1. Life Experience (sometimes used with "ever" and "never")

Have you ever been to Pluto?

No, but I've been to the toilet.

2. Change in Situation (sometimes used with "just" and "already")

Call a doctor! I've just cut off my ears!

Don't call the doctor. I've already sewn his ears back on.

Note that this doesn't have to be a fast change or a recent change. We can use it like this:

The Earth is a crazy place because life has evolved here.

The important idea is that a change has led to the present situation, like something casting a shadow.

3. Up to Now (sometimes used with "yet")

You've had that hat on for five days, but you still haven't put on your pants.

Have you spray painted some pants onto him yet?

You can use two or three of these together, too.

It's his first day of school and he hasn't learned to speak yet, so the teachers are disappointed.

The above example talks about Life Experience, Up to Now, and even a Change in Situation.

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Other uses of Perfect tenses are generally used for the same reasons.

For example, here are examples related to the ones above, for the same three uses (Life Experience, Change in Situation, and Up to Now):

When you went to Pluto, had you ever been there before? Or had you only been to the toilet?

(For this Change in Situation example, I'll use Reported Speech / Indirect Speech.)

Marge told me to call a doctor, because she'd just cut her ears off. But Hector told me not to call the doctor, because he'd already sewn her hears back on.

Hector is really amazing.

Let me also address the Earth example:

The Earth was a really crazy place before Ming destroyed it, because life had evolved there.

Last, but not least:

Charles had worn that very tall hat for five days and hadn't put on his pants. Had Susie spray painted pants onto him yet? No, she hadn't, but she had been thinking about it...

This leads into one last point I'll address in brief (because it's a larger topic), which is adding in the Continuous tense, the "-ing" tense. This means that we use a form of be plus the Present Participle (the "-ing" form).

If we use a Perfect Continuous tense, we use "has/have been" + VERBing.

If you have been paying attention, you may now be interested to know how this is different.

In general, the Continuous aspect indicates that a verb is active now and not complete within the time we're describing. We may use it to emphasize that the verb is temporary, to indicate that it's something in progress (from one state to another), to convey repetition, and/or to emphasize activity.

Rather than give more rules, I will leave you with a few examples with some context suggesting what additional information the Continuous aspect conveys. This is not absolutely complete, but is plenty to be useful.

Last year my friend invited me to move to Mars with her. I'd never lived on Mars before, so I'd been hearing good things on the news about it and I decided to give it a try. I'd lived on Earth all my life, and for two weeks I had been living with my parents, so I was ready to move. By the time we finally reached Mars, we'd been flying for two weeks. (Years ago it took much longer to reach Mars, but a new startup had been studying antimatter fuels and had invented a much faster rocket.) Soon after we'd arrived, I started to wonder why I'd been looking forward to the trip so much...

"I'd been hearing" suggests repetition. "I'd been living" suggests that the living arrangement was temporary, and subtly suggests that the speaker had been hoping to leave, rather than stay for years.

Answer 3

The past perfect is used to connect or relate one past action to another more recent time or action in the past. This sequential relation is often established between clauses with the past perfect where the past perfect is the first action and the second is expressed in the past simple. It is required when the conjunction used to link the two clauses does not indicate a sequence and the clauses are not in sequential order. There is often a consequence to that relation that is either explicit or implied when this tense is used.

The past perfect and the simple past sequence actions that occurred in the past. The past simple does this by the explicit order of the verbs/ clauses - from earliest to latest.

I got in the car, (and I) drove to the market and (I) bought some bananas.

The parentheses indicate ellipsis, which is optional.

You wouldn’t use the past perfect in a sentence like this, it’s just about sequence of actions and the simple past is used for this purpose.

*I had gotten (or got if your British) in the car, drove to the market and bought some bananas to make banana splits. (incorrect use of the past perfect)

It makes no sense to use the past perfect, when the clauses are already in sequential order - just use the past simple.

Sequencing can be done in that past simple with different conjunctions like before and after - and since they provide sequencing, the clause order can change and the sequence is still clear. I drove to the market after I got in the car. I drove to the market before I bought some bananas.

Some conjunctions are explicit in their sequencing while others are much less indicative of the sequence of actions.

For example, when as a conjunction/ time word, doesn't indicate sequence very well.

I left the market and began the drive home *when my wife called to tell me she also needed ice cream.

At best this sentence (with when) is ambiguous. The sequence is not clear and the sentence could be interpreted to mean that the subject simply left the market just after his wife called, or that he left before she called. But with the conjunctions and, then, and then, before or after, the ambiguity is resolved.

I left the market, (and I) began the drive home and my wife called to tell me she also needed ice cream.

I left the market, (and I) began the drive home before my wife called to tell me she also needed ice cream.

I left the market, (and I) began the drive home after my wife called to tell me she also needed ice cream.

The present simple in joined clauses is about sequence, there’s really no implied consequence and no need for the past perfect.

When is properly used to indicate simultaneous or virtually simultaneous actions (one thing happens immediately after another).

Watch what happens when the clause order is changed.

When my wife called to tell me she also needed ice cream, I left the market and began the drive home. (immediate sequence)

This sentence has clear meaning and clear sequence - it just sequences the actions, and you can’t reverse the order of the clause without creating ambiguity. This a different sequence than in the previous sentences and and when indicates that the second action happened immediately after the first.

Now let’s see what happens with the past perfect.

I had left the market and begun the drive home when my wife called to tell me she also needed ice cream.

The sequence of actions is established by the use of the past perfect and the ambiguity of when does not arise. But it’s about more than sequence. The implied consequence is that the subject had to return to the market for the ice cream, or that they would have bananas and no ice cream. The sequence could be easily established with the simple past but not the implication.

You can change the order of the clauses and still get the same meaning.

When my wife called to tell me she also needed ice cream, I had (already) left the market and begun the drive home.

No problem with sequence and the same implication applies.

You can use the adverb already if you want but the tense implies this meaning anyway, so it is not required. The past perfect sequences without needing to use an explicit order to the clauses because the past perfect is always the first action.

When I arrived everyone had left.

Everyone had left when I arrived.

The meaning of these sentences would change drastically if both clauses were in the past simple. In a structure like this (with when) the past perfect is required for the intended meaning. Without it, and using the present simple, the actions are barely sequenced and indicate practically simultaneous actions and imply a causal relation between the clauses. The order of the clauses does not change the meaning.

When I arrived, everyone left.

Everyone left when I arrived.

But you could also get the same meaning of the past perfect using a different time word without the past perfect.

Everyone left before I arrived.

Before I arrived, everyone left.

I'm not sure that the second sentence here is grammatical. I would accept it but would also leave it to others to argue.

Let’s see what we can observe with another sentence.

He had tried to reach her a few weeks before the wedding.

He tried to reach her a few weeks before the wedding.

In these two the preposition before takes an object not a clause but it still indicate a time relation and sequence - the call happened before the wedding.

A few weeks before she arrived for the wedding, he tried to reach her.

A few weeks before she arrived for the wedding, he had tried to reach her.

He tried to reach her a few weeks before she arrived for the wedding. He had tried to reach her a few weeks *before *she arrived for the wedding.

In all of these sentences the preposition before (also a conjunction in the last two) takes care of the sequencing so the past perfect is not required in any of them. But it is not ungrammatical to use it if you want, though it makes little difference in the meaning of the sentences. The only difference is that the past perfect implies a consequence in the relation, whether it is expressed or not, and the simple past simply states the fact that these actions happened in sequence.

Hope that helps.