In the following example, the verb in the subordinate clause following "would know" is backshifted:

CIRCUS Manager:“All you have to do is look the lion in the eye and show him you're not afraid.” Assistant: “Yes, but the lion would know I was just being deceitful.”

But, I also found the following sentences in English grammar text books:

It would seem there has been a mistake.

One would suppose the danger is over.

I should say that this book meets your requirements.

I should think it's going to rain soon.

What is the rule of tense backshift in a subordinate clause following a past form modal verb?

  • In the second block-quote those aren't past tense verbs IMHO, they either express subjunctive ("it would seem" and "one would suppose"), or simply modal. Commented Oct 5, 2015 at 12:40
  • 4
    By the way, "I should say…" and "I should think…" in this context are perhaps a bit formal or archaic. I nearly never hear people use "I shall" in its sense synonymous with "I will". The exception is "I should think not!" or "I should think so!" as an exclamation. For your third sentence, I would personally say "I'd say that this book meets your requirements" as a contraction of "I would", or "This book might meet your requirements", or "I imagine [that] this book meets…". For the fourth sentence, "I think it's going to rain soon", or "I imagine it's going to rain soon". Commented Oct 5, 2015 at 12:48
  • In fact, I'm pretty sure the "lion would know" and "I was just being deceitful" in the given example are subjunctives rather than backshifted into past tense as well... Were it only that we had separate words for those constructions in English.
    – Jez W
    Commented Oct 14, 2015 at 12:19

3 Answers 3


The first example you give is actually a past conditional construction. The "Yes, but" in the first example basically skips a conditional phrase, making it essentially a form of:

If I did that, the lion would know that I was being deceitful.

An alternative form, where there isn't any shifting, would be:

If I do that, the lion will know that I am being deceitful.

In this case, the verb "to be" isn't modified by the "would" directly per se, but the tense is changed to match the rest of the sentence.

Unfortunately, unlike some other languages, in English there often isn't any distinction between the subjunctive/conditional form of a verb and the past participle, so it can sometimes be tricky to tell which is being used in a given sentence.

As for the other examples:

It would seem there has been a mistake. Here "has been" is actually unmodified, as the mistake occurred in the past. You could equally say "It seems there has been a mistake".

The remaining ones are also unmodified, and as was mentioned in one of the comments, the "should" or "would" are basically particulate constructions - so you might occasionally hear them spoken colloquially, but they are really just there for emphasis and could just as well be left out (especially in the case of "I should think it's going to rain soon", which is synonymous with just "I think it's going to rain soon").

It should be noted, though, that the two involving "would" could also be used in a conditional sense - and if so, then the following verbs would also be modified similarly:

If he covered his tracks well enough, it would seem as though there had been a mistake in the investigation.

But generally speaking, "It would seem" and "I would think" are just common turns of phrase that don't take any modification - the "would" only serves as emphasis.

  • I know we can add a clause like "If I did it" before the sentence to complete so called second conditional sentence. The problem is if the shift from "will" to "would" automatically cause the shift from "am" to "was". As for the use of the term "subjunctive", I quote from The Oxford dictionary of English Grammar in the comment below.
    – Aki
    Commented Oct 15, 2015 at 5:22
  • : Traditionally, the uses of ordinary indicative tenses to express hypothesis etc., like, for example, the use of a past tense to refer to a present or future condition (e.g. If you came tomorrow . . . ), have been described as examples of subjunctive mood or tense— perhaps because in translation such a usage might need a subjunctive form in another language. Modern grammar considers this to be quite unjustified, and restricts the use of the term subjunctive to two distinct tenses (as follows)...
    – Aki
    Commented Oct 15, 2015 at 5:24
  • I can't find that particular quote - but also from the Oxford Dictionary: oxforddictionaries.com/words/moods (where the term "subjunctive" is used to refer to exactly that kind of construction). In contexts like this, I would say that yes, the same thing that causes the shift from "will" to "would" necessitates "am" becoming "was".
    – Jez W
    Commented Oct 15, 2015 at 8:54
  • 1
    Because in the most common interpretation of "would seem there has been a mistake", it's neither a subjunctive nor a conditional construction - "would" here is an optional word added for emphasis as part of a turn of phrase, the same as with the other three examples in the second box (so here, "would seem" is synonymous with just "seems"). (Note that "would seem" could also be used conditionally - and were it part of a conditional sentence, it would indeed take "had" after it rather than "have").
    – Jez W
    Commented Oct 15, 2015 at 11:30
  • 1
    Maybe not impossible, but I think "was" would be preferable (I can't think of any case where "the lion would know" could be interpreted to be anything other than part of a conditional - and so "am" would also be modified to "was")
    – Jez W
    Commented Oct 15, 2015 at 12:52

Here's a tip on learning English grammar: English doesn't work by rules. English has a small number of modal verbs and grammatical inflections, with which speakers struggle to communicate a large number of grammatical distinctions. People do their best to suggest whatever temporal distinctions are relevant in a specific situation. The rules in grammar books are just approximations for the many ways in which people try to milk too-few grammatical forms for too-many grammatical distinctions. If you remove the word "backshifting" from your vocabulary, you might find English grammar a little easier to sort out, because you won't be tempted to search for a rule that isn't there.

The way you have to improvise with English tenses is best learned by many examples, preferably in some context that makes them meaningful. Here is one of your counterexamples analyzed, with a little context added:

"It would seem there has been a mistake," said Rupert, looking at the ten-foot-high pile of gravel that had been dumped on the lawn.

Rupert uses the present perfect has been is to indicate that the mistake is relevant now (when Rupert is speaking). The mistake—pouring gravel on the lawn—was made in the past, but the problem of cleaning it up is the salient fact right now. This is a typical case for using the present perfect.

The word would is not being used here to indicate the past tense. Technically, would is the past tense of will, but here it indicates the consequence of a hypothetical condition—in the present. You see how would has more than one grammatical meaning? There is no hypothetical condition stated explicitly. Implicitly, the hypothetical condition is "if the obvious inference that someone dumped a pile of gravel here by mistake is true." In this example, would is chosen for understatement. In many situations where would lacks a condition and describes the present, it's chosen for politeness, since the conditional mood "softens" a statement.

Now here is the original example:

Circus manager: “All you have to do is look the lion in the eye and show him you're not afraid.”

Assistant: “Yes, but the lion would know I was just being deceitful.”

In this example, too, would indicates the consequence of a condition: "If I looked the lion fearlessly in the eye, it would know I was just being deceitful." The assistant is describing a hypothetical future situation.

The reason for choosing was is because "I (am) just being deceitful" is meant in the subjunctive mood. The subordinate clause describes a hypothetical consequence, which the assistant wants to avoid treating as a real situation. A common way to make a future subjunctive in English is to put the verb into the past tense. Thus you see another way that English makes do with a shortage of grammatical forms. This use of the past tense for the future subjunctive works because a listener understands that the sentence is about the future.

Notice that I put "If I looked the lion in the eye…" into the past tense. The same principle is at work. The principle isn't "under such-and-such conditions, you must backshift", it's "English lacks a future subjunctive, and I want to be clear that I mean this verb subjunctively, so I'll just co-opt the past tense to indicate the subjunctive mood. People do that frequently enough that you'll recognize the construction, though it's not a rule."

P.S. Here's another answer, which explains at length how speakers bend would and should to serve many grammatical roles—not following rules, just making reasonable choices among the available words in a wide variety of situations. People choose the tense of a subordinate clause to suggest or reinforce the intended meaning, not according to a rule like "Past-tense modal verbs require subordinate verbs to shift tense."


This link explains well the rules for backshifting as well as exceptions where backshifting may not be necessary.

Typically, backshifting is used in cases of indirect or reported speech. However, there are other scenarios where backshifting is used:

"Backshifting occurs not only with indirect speech, but also with reported feelings and thoughts expressed frequently with verbs such as know, think, realize, and forget.

(19a) She knows that we are meeting tomorrow.
(19b) She knew that we were meeting tomorrow.

In (19a) the reporting verb (knows) is in the present tense, as is the verb in the reported clause (are). In (19b), when the reporting verb is past tense (knew), the verb in the reported clause is backshifted to past tense (were). Note that the time of the situation ('we are meeting') has not changed; it remains in the future." (Dee Ann Holisky, Notes on Grammar. Orchises Press, 1997)

Further, the rules for backshifting and modals are elaborated in this link.

You may also browse this question thread on ELL on backshifting and reported context. There's another question thread on mixing tenses in reported speech.

  • How can I explain the difference between the first block-quote and the second block-quote? That is my question. The sentence in the first block-quote seems to be following the backshifting rule "will know I am" -> "would know I was". But the sentences in the second block-quote don't.
    – Aki
    Commented Oct 10, 2015 at 11:23
  • Your original question asked for rules. I have shared some of the rules. We use backshift when it is logical to use backshift. Check for elaboration in the link I shared in the answer.
    – Mamta D
    Commented Oct 12, 2015 at 6:16
  • My original question is "What is the rule of tense backshifting in a subordinate clause following a past form modal verb?", not about the general rule of backshifting. I've already checked the links you suggested. But, I couldn't find the explanation for my question.
    – Aki
    Commented Oct 12, 2015 at 14:45
  • In that case, these links may prove useful though they don't actually list any rules: grammar-quizzes.com/modal2b.html and english.stackexchange.com/questions/10054/… and ell.stackexchange.com/questions/22920/…
    – Mamta D
    Commented Oct 13, 2015 at 4:01
  • Thank you for further links. Unfortunately, I couldn't find the answer there too. I'll try another grammar book.
    – Aki
    Commented Oct 13, 2015 at 15:38

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