Sequence of tenses

The sequence of tenses is the name given to a simple rule governing reported speech.

Direct and indirect/reported  speech

Reported or indirect speech involves, simply, the reporting of a statement that was once in quotation marks. Reported speech will have two clauses: a main clause of saying/speaking/reporting;  and a dependent clause referencing the original statement. For instance:

"I am king of the jungle."  This is a direct quotation, or direct speech (i.e. it is between quotation marks).

Tarzan says [that] he is king of the jungle is indirect or reported speech. You may include or leave out the word "that" as you prefer. Usually it is omitted.

The main clause is now:  He says; and the dependent clause is: that he is king of the jungle.

"I am going to listen to some electronic dance music."

This becomes: He says [that] he is going to listen to electronic dance music.

Sequence of tenses

If, however, the verb in the main clause is in the past tense (He said), then we must modify the verb in the dependent clause to match it.

Thus we have:

He said [that] he was going to listen to electronic dance music.

Similarly:

"I have never seen such a silly dance" becomes: He claimed  [that] he had never seen such a silly dance.

In a sequence of tenses, the future becomes the conditional (will becomes would):

"I will tell her when I meet her this evening."

He promised [that] he would tell her when he met her this evening.

Now consider this:

"I love  you, Margaret."  Noble words, spoken on a Wednesday. On the following Tuesday, the man informs us: Last week, I told Margaret [that] I loved her.

This is correct. Since the verb told is in the past, the dependent verb loved is also in the past.

However, fearful that we might understand that this is how he felt last week only, and that we will infer that he possibly stopped loving  Margaret by the end of the week, the man might break the rule and say, Last week, I told Margaret that I love her.

The speaker is anxious to keep love in the present tense to avoid  giving the impression that his passion has suddenly faded. This is all right. The rule can be broken to avoid misunderstandings and divorce.

The rule of the sequence of tenses will often be broken when the dependent clause refers to something that continues to be just as true in the present as it was in the past.

Accordingly, "The  earth goes round the sun and the moon goes round the earth" is the sort of statement that remains true no matter what the time reference, and we should therefore say:

I taught my students that the  earth goes round the sun and that the moon goes round the earth.

Most grammar books recommend this, and most people think it sounds more natural. After all, if you say I taught my students that the earth went round the sun and the moon went round the earth, you might be implying that this is no longer the case.

To prevent this misapprehension, the grammar books tell you that the sequence of tenses rule here does not apply.

I do not agree. I explained that the earth went round the sun sounds absolutely fine to me.

The claim that this sentence is ambiguous depends on the listener being impressionable enough to believe that God might have issued a decree last Friday instructing the sun to start circling the earth. I would argue that any intelligent listener or reader should be able to understand that the past tense in the dependent clause is a result of the verb explained  rather than of any changes to the rules of astronomy.

True, this may be just my way of thinking, but the problem I most frequently encounter is not that students are too literal in their application of the sequence of tenses, but that they fail to apply it at all.

It is better to err on the side of excessive enforcement of the rule than to ignore it altogether, I feel.