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Concourse 2

Modality: tense and aspect


Before you tackle this guide, you should be confident that you are familiar with the contents of the essential guide to modality and the guide to pure modals.
You should also, of course, be familiar with the distinctions between time, tense and aspect.



English modal verbs are often described as defective, meaning that they cannot be used with the full range of inflexions or in the full range of tenses that lexical or main verbs allow.
For example,
smoke, go, enjoy, imagine, come, decide, think, spin etc. are all non-defective, lexical verbs and change form to show:

  • Person
    I smoke, she smokes
  • Tense
    I come, I came, I imagine, I imagined
  • Aspect
    I decide, I am deciding

Modal auxiliary verbs cannot be treated this way (*I musted, *He musts, *I am musting etc.)

Unlike many languages, English has few natural past-tense forms for modals verbs.  There is, for example, no simple past-tense way of expressing
    I must go now
If we want to put it in the past, we are obliged to use somewhat clumsy formulations such as
    I had to go then
    He said he had to go then
    I was obliged to go then

and so on.
Equally, when we use reported or indirect speech, we are often forced to substitute modal verbs with other expressions and report, for example:
    You may go
    He gave me permission to leave
    He said I might go
is another possibility.
See the guide to reported speech for more on how we cope with the difficulty of reporting modal expressions like these.

Here's the list of modal verbs, taken from the essential guide to modality showing which do and which do not have past-tense forms:

Present Past
can could
may could / might
shall should
will would
must (had to)
---- used to
ought to ----
need ----
dare dared

The verb had to is shown in brackets because it is actually non-defective and can be altered for tense and person:
    She has to go
and for aspect
    She's having to work long hours
    She has had to work long hours
    She will have to work long hours
The verb be able to is similar although it does not permit the progressive particle.  We can have:
    He was able to open the case
    We had been able to open the case
    He will have been able to open the case

but not
    *He was being able to open the case
or any other progressive , continuous or durative -ing form.
Other languages are more obliging and have forms of modals or modal expressions akin to canned, musted etc. to express past obligation or past ability or will must, will can to express future ideas.

This is not to say, of course, that English is incapable of expressing the ideas of tense and aspect with modal verbs.  However, the ways it is done are often complicated and difficult to learn.  For example:

Past permission and prohibition: I was allowed / permitted to ...
I could ...
It was forbidden to ...
Note that *I can have helped is not available as the past of I can help.
Past ability: I was able to ...
I could ...
I had the ability to ...
Again, *She can have climbed the wall is not an available option as a past form of She can climb the wall.
Past volition: He said he was willing to ...
She was happy to ...
The past of the volitional use of I'll make the dinner is not available as He said he'll have made the dinner because that carries a future perfect meaning.
The past form would is an available option which occurs in contingent (conditional) clauses but often without the sense of volition except in indirect speech.

In summary, past ability, past permission and past volition are not normally expressed using a perfective aspect.


Which modal ideas can be used with aspects?

Some types of modality can be expressed using aspect of the modal verbs.  For example, we can say:

Perfective aspect: She will have missed the train
She might / could have missed the train
She can't have missed the train
He shouldn't have said that
He needn't have gone
She can't have arrived yet
Progressive aspect: She must be getting tired
They might be arriving late
I may be travelling for work
You can't still be working
He shouldn't be smoking
He can't be working at this hour
You should be working less
Combined perfective and progressive aspects: She must have been getting tired
She shouldn't have been working so long
They can't have been working hard enough
They shouldn't have been playing by the river
They might have been arguing
They oughtn't to have been sleeping
For more on the distinction between perfect aspect (i.e., a relational tense form) and perfective aspect (i.e., a finished, absolute sense) see the guide to time, tense and aspect.


Identifying types of modality

The trick, of course, is to identify the types of modality that can be used in this way and those that can't.  To do that, we need a little logical theory.

speculation and deduction
this is called epistemic modality because it refers to the speaker's viewpoint regarding the truth or otherwise of a proposition.  From the table above, these are examples of epistemic modality, expressing various degrees of confidence:
    She will have missed the train
    She might / could have missed the train
    She can't have missed the train
    She can't have arrived yet
    She must be getting tired
    They might be arriving late
    I may be travelling for work
    You can't still be working
    He can't be working at this hour
    She must have been getting tired
    They can't have been working hard enough
    They might have been arguing
degrees of obligation
this is called deontic modality because it concerned with duty or obligation (or the lack thereof).  From the table, these are examples of deontic modality expressing varying degrees of obligation:
    He shouldn't have said that
    He needn't have gone
    He shouldn't be smoking
    You should be working less
    She shouldn't have been working so long
    They shouldn't have been playing by the river
    They oughtn't to have been sleeping

There are two other types of modality which do not normally occur with the perfective, progressive or perfect aspects:

  1. alethic modality
    This refers to truth of propositions in the sense that something is necessarily rather than deductively the case.  For example:
        Iron must be heated to 1,538°C to melt
    This cannot be referred to as
        *Iron must have been heated to 1,538°C to melt
    because it is a necessary (i.e., always true) property of the element.
  2. dynamic modality
    This refers to modality centred on the subject.  For example:
        I can see the mountains
    and is not to do with external obligations, duties or a view of the truth of a proposition.  We can have, e.g.:
        I could have swum across the river
    but only in the sense of an unfulfilled ability.  If we say, e.g.,
        She could have swum across the river
    the hearer will understand that we are referring to a possible event (i.e., epistemic modality), not a past ability.  For past ability, we would use the past tense of can and have:
        She could swim across the river
    or the replacement form
        She was able to swim across the river

For more on the types of modality referred to here, see the guide to types of modality.


Perfect and perfective aspects

It is important to understand what the modal verb + have + past participle is actually implying in terms of aspect.
If you have followed the guide to aspect on this site, you will be aware that the view taken here is that a sentence such as
    He has arrived
is actually a present tense form with a perfect aspect.  In other words, the have + participle refers to the present in relation to the past.  The present perfect is a relational, present tense.

Unfortunately, when we are dealing with modal concepts, that definition of the function of the structure is only partially true.  Here are some examples to explain:

Example Explanation
She might have missed the train and still be at the station This is a true perfect aspect of the verb phrase because it refers to the present in relation to the past.
He shouldn't have said that and upset her so This is, in fact, a perfective past form.  Both the saying and the upsetting refer to events and states in the past.  We can add a fixed time phrase such as last week to this sentence.
He needn't have gone but he did This is another perfective past form.  The lack of obligation and the going are both in the past and may or may not have any relation to the present.
She can't have arrived yet This is a perfect aspect referring to the temporal relationship between an event and a current state.  The non-arrival (up to now) relates to the fact (in the present) that she is not here.
She could have arrived before me The use of could in this sense is perfective when we are referring to ability or possibility.  We may, in fact, be talking about events far in the past which bear no relation at all to the present.
She must have been getting tired and probably fell asleep Here we have another perfect aspect but one which relates a past event to a previous past state.  It is paralleled by, e.g., She had got tired and fell asleep.

In summary, the general distinction between relational tense forms (perfect aspect) and absolute tense forms (simple aspect) breaks down when modality is considered.
This is a key teaching point because the rule of present relevance signalled by the have + participle form no longer consistently applies.
For more on the distinction between relational and absolute tenses in English, see the guide to time, tense and aspect.

progressive etc.

Progressive and other aspects

Reassuringly, even with modal verbs, the distinctive uses of the be + -ing formulation remain intact.  Here are some examples:

Example Explanation
She must be getting tired This is a continuous aspect, referring to a state rather than an event.
They might be arriving late This is a prospective aspect referring to a future based on present data.
I may be travelling for work This is an iterative sense referring to a repeated (but not current) action.
You can't still be working This is a true progressive aspect referring to an action in progress.
He shouldn't be smoking This is a habitual aspect referring to a current routine.


Passive constructions

Passive constructions are available in English for both types of modality and for both aspects.  For example:

Example Explanation
The house should have been finished by then Passive perfective but used for both past and future with a change in the types of modality:
Epistemic modality: I am speculating that the house is in fact finished.  The implication is that I am speaking about the future in relation to what came before it (compare the greater certainty of The house will have been finished by then).
Deontic modality: I am stating that there is or was an obligation of some kind that the house was finished.  The implication is that the house is not in fact finished.
The house might have been finished This is epistemic modality only.  It is speculation about the present state of the house.
The house should be being finished Like the first example, this can be speculation concerning what is currently taking place (epistemic modality) or implying an obligation that work is being done on the house now (deontic modality).
The house may be being finished This is epistemic modality only.  It is speculation about the present state of work on the house.  It can be replaced with could with little or no change in meaning.  In this case, could is only speculative (epistemic) and not to do with ability (which would be dynamic modality).
The house should have been being finished This is a combination of the passive with both a progressive and perfect aspect and is quite unusual.  It is an available construction in English (and should is replaceable a range of other modal verbs to make different types of modality).  Some consider it clumsy at best, wrong at worst.


Teaching in this area

There is ample scope for confusion in this so things have to be taken carefully.  A first rule of teaching is not to overload learners and a second is to distinguish very carefully between the types of modality which can be used with the perfect or perfective forms.
It is, of course, not necessary to burden learners with terms such as epistemic modality but, in order to be clear and helpful, teachers need to be aware of the meaning of the terms and select targets and settings in which the modality is clear.

The final important thing to note is that the form which appears to be a perfect aspect, e.g.:
    I might have told him
is, in fact, often perfective (i.e., finished and fixed in time) and unrelated to the perfect aspect of, e.g.:
    I have told him
which refers to the fact that he currently knows whatever it is.
This is not at all easy to grasp.  Learners who have taken pains to assimilate the concept of the relational nature of perfect aspects may be bewildered to discover that it no longer applies in many cases.


Teaching ideas

If you refer to the guide to teaching modality, you will find a number of teaching ideas evaluated in terms of their clarity and efficacy.  The key point is to distinguish the type of modality which is being considered.  Mixing them up will cause a good deal of confusion, not least because some of your learners' first languages may reserve particular verbs or structures for each type of modality.

for epistemic modality
Deductive procedures such as the ones outlined in the guide to teaching modality are fruitful providing the level of (un)certainty is clearly identified.
For future time, speculation exercises are common and science fiction can be an engaging focus.  Topics typically include:
    What do you think your home town will be like in 20 years' time?
    What technology do you think will be available to your grandchildren?
    What do you believe cities of the future will be like?

Younger students can be encouraged to think about their own futures.
All these questions contain a verb process realised by verbs like think or believe.  That's important or the response will simple be a future perfect form expressing too much certainty.
However, as is the case for deduction settings, the degree of certainty signalled by the modals and intonation / stressing is a key consideration.
In the past, epistemic modality (e.g., for deduction based on current evidence) can be practised with the use of accident- or crime-scene graphics to elicit, for example:
    The burglar must have come in through the bathroom window
    The driver of the red van can't have been looking
    He might not have indicated
    He must have been in the bedroom

If you would like to download a lesson using the crime-scene idea at B2/C1 level, click here.
for deontic modality
The telling of a story containing many instances of poor judgement calls is an engaging procedure.  For example, the following story read aloud quite slowly with pauses to allow interruption using shouldn't have ... can work well:
When I landed at Heathrow, I left my coat on the plane because I knew it's always warm in London.  After that, the first thing I did was light a cigar and take a few photographs of the arrivals hall.  When my turn came to have my passport checked I refused to hand it over and told the woman she looked silly in her uniform.  Before I left the airport I decided to leave my luggage behind in an airport café because it was too heavy to carry and then I started to walk to central London.
The types of responses one hopes for are, e.g.:
    You shouldn't have done that; you should have ...
This can be combined later with expressions of epistemic modality along the lines of:
    You shouldn't have done that because she might have got very angry
Learners can be further engaged by getting them to write their own silly stories and reading them out for others to comment on.  Possible topics are:
    A disastrous holiday choice
    A dreadful dinner party with the wrong guests sitting together


Related guides and links
essential guide to modality a simpler guide in the initial training section
pure modals a traditional view taking each modal in turn and identifying its function
semi-modal verbs a guide which also considers marginal modals such as seem, tend, be about to etc. alongside the true semi-modals, need, dare, used to.
time, tense and aspect this is the place to go if the distinctions between, e.g., perfect and perfective, continuous and progressive are obscure
complex tenses which also considers complex tenses in relation to modality
teaching modality for some more ideas transferable to the analysis above
types of modality for more on types of modality mentioned here such as epistemic and deontic
modality index for links to guides to other areas of modality