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Concourse 2

Epistemic modality: degrees of likelihood

That must be her brother

You may find epistemic modality referred to as propositional modality because it refers to the speaker / writer's view of the truthfulness of a proposition.  We don't use that term in this guide but it is an alternative.

The example above is just one way in which a speaker / writer can express the belief that a proposition has a high likelihood of being true.  The truth or otherwise of propositions is what epistemic modality is about (from the Greek epistēmē (knowledge)).
In this example, we have used a modal auxiliary verb (must) to express a high degree of likelihood and we can substitute others such as may, could or might to suggest lower levels of likelihood.
There is, however, a range of other ways to express the same viewpoint.  Here are some examples.  Your task, should you choose to accept it, is to divide them into 4 categories (there are two examples of each).
Click here when you have an answer.


Where's the evidence?

The car must have come this way  

All four of the ways of expressing the speaker's view of a proposition's truth or likelihood can be used to express a range of types of epistemic modality.  Following Palmer (2001) there are these:

in which the speaker indicates that he or she is simply guessing about the likelihood of a proposition being true.  For example:
    Mary might be in the garden
    Mary is possibly in the garden
    I'm guessing that Mary is in the garden
    I imagine Mary's in the garden

    I doubt if he's at home
    She might not want to come

In all these cases, we can paraphrase what is said as:
    This is a possible but by no means certain conclusion.
This is sometimes referred to a judgemental modality because it concerns the speaker / writer's judgement alone.
in this case the speaker indicates that there is evidence to back up what is said and the proposition has, therefore, more chance of being true.  For example:
    Mary must be in the garden
    Mary's certainly in the garden
    I'm quite sure that Mary's in the garden
    I conclude that Mary's in the garden

    That can't be true
    Mary won't be at home at this time

In all these cases, we can paraphrase what is said as:
    This is the only possible conclusion from the evidence we have available.
This is sometimes referred to as evidential modality when what is said or written includes some notion of an assessment of the evidence as in, for example:
    It's very cold in there so the heating can't be on.
in this case the speaker is indicating not that he or she is working on clues and evidence but that the proposition will be true because of what is generally known about the situation and the people involved.  For example:
    Mary will be in the garden at this time
    Mary's always in the garden at this time
    We can assume that Mary's in the garden
    I assume Mary's in the garden

    Mary won't be at work on Sunday
    They won't be having dinner at this time of day

In all these cases, we can paraphrase what is said as:
    This is a reasonable conclusion to draw from what is generally known.

For teaching purposes, this is a useful three-way distinction to make because it allows us to present and practise the forms and realisations discretely without getting confused about what is intended in terms of the speaker's implications and what the hearer can infer.



English, in common with a very wide range of languages has no special grammatical form which allows the speaker to signal that a statement is dependent on hearsay or personal assumption concerning its truth or likelihood.
Some languages, Japanese, for example, do have an evidential form of the verb, often signalled by suffixes or other verb-form changes.  Arabic has a range of particle additions to the syntax which can signal various levels of certainty.
One estimate, Aikhenvald (2004), suggests that around 25% of all languages have evidential forms.

In English, therefore, evidentiality is often signalled through the use of disjuncts such as:
    I hear that he's lost his job
    I see that you have a new car
    I think that its going to rain
    As I hear it, the road will be closed
    As far as I understand, the figures will be ready tomorrow
    As far as I know, that's the situation
    They say he's pretty wealthy
    It is said to be expensive
    It seems the train will be on time
    it seems to me that the work is poorly done
    It looks like / appears it's going to rain
    Allegedly, she's being investigated
    Reportedly, that's a good solution
    Obviously / Clearly / Apparently / Seemingly / Patently
etc. that's wrong

Clearly, there are semantic issues rather than grammatical ones, concerning the strength of the likelihood which users of the language suggest in their choice of disjunct.
Stressing a part of the disjunct usually lowers the estimation of certainty so, for example:
    They say he's pretty wealthy
emphasises the conclusion that he probably is wealthy, but
    They say he's pretty wealthy
reduces the certainty.
When it is present, emphasising the pronoun as in
    As far as she knows, it's OK
removes the onus from the speaker concerning the truth of a proposition.

This is a teachable area which does not depend on mastery of modal auxiliary verbs with their connected structural and semantic problems for learners but one which can significantly enhance the range and precision even low-level learners of English can use.


Overlapping categories

One other sort of modality overlaps epistemic modality and this is what is known as alethic modality (from the Greek word for truth, alēthia).

Usually, alethic modality expresses that which is necessarily true by the way the world works.  For example:
    A square must have four sides
    Parallel lines cannot meet
    Lead will melt at 327.5°C

    Parliament meets in Westminster
and so on.

Epistemic modality is also concerned with the truth or otherwise of a proposition so it is easy to see where the overlap occurs.
The difference, however, lies in the view taken of a proposition:

View 1: the world of the observer
In this case, it is the language user's world in which the truth or otherwise of a proposition is set.  For example:
    John must be at home by now
    You can't be serious
    That's probably not true
    This is certain to be the right train

All these statements apply not to all possible worlds but only to the world of the participants in the exchange of meanings.  In none of these cases can it be said that we are referring to truths outside that sphere.
View 2: all possible worlds
Leaving aside the genuine possibility of other universes in which the laws of physics and mathematics are different, statements from this standpoint refer to universal truths, not truths contingent on the setting.  So, for example:
    Early humans must have developed bipedalism
    Humans cannot breathe in a vacuum
    Vertebrates must have backbones
    17 is a prime number

and so on.
None of these statements is dependent at all on the environment of the participants in an exchange and none is contingent.
The present simple form of the verb is often used to express alethic modality because, in English, it carries the sense of timelessness.

Some languages, English not being one, reserve a different form of modality to distinguish between alethic and epistemic modality.

Alethic modality is considered slightly more fully in the guide to deontic modality, linked below, because there is also an overlap between obligation and necessity.


Seeing the wood for the trees

We can take the four categories we looked at above one by one to do a bit of analysis.  There's a good teaching reason for doing this, of course, because it focuses you and your learners on one style of epistemic modality at a time and allows people to 'see the wood for the trees'.
It also helps you plan and analyse the language before you plunge in.
Mixing up the four main ways to express likelihood in the classroom is not a good way to present and practise the area because languages vary in what's possible and what's natural.  It can confuse and bewilder and that's unhelpful.


Modal auxiliary verbs

What's that?!  

The issue here is the strength of the modal auxiliary verbs.  Some coursebooks and many teachers are tempted to invent some kind of cline between 0% and 100% likelihood of something being true.  The verbs and other expressions are then placed on the cline where the teacher or course-book writer believes they ought to go.  There are problems with this approach because:

  1. it is almost impossible to get two native speakers to agree exactly where on the cline each verb should go
  2. as we saw above, intonation and stress play a crucial role in expressing meaning.  Stress a verb like must and you increase the certainty, stress a verb like might and you decrease the level of certainty
  3. the real difference is not in the level of certainty itself but in the level of certainty of whether something is true or not true.

A better approach is to consider three levels of likelihood and divide the expressions into positive and negative propositions.  Here they are, expressed without using modal auxiliary verbs:

There is some utility in having a template scale such as:


on which you can hang the modal auxiliary verbs and other modal expressions but it needs to remain mobile so that you can move things to show how stress and intonation can affect how strong the expressions are and whether it increases or decreases the level of certainty communicated.

This is not the point to consider in any detail all the possible modal auxiliary verbs used in this sense.  There are guides elsewhere on the site for that.  Go to the overall map of modality, linked below, for more and navigate to what you want from there.

Now pause for a moment and consider which modal auxiliary verbs are used in each case.  There are six choices:

  1. high likelihood something is true
  2. high likelihood something is not true
  3. mid likelihood something is true
  4. mid likelihood something is not true
  5. low likelihood something is true
  6. low likelihood something is not true

Click here when you have a list.


Sources of potential confusion with modal auxiliaries


Modal adjuncts and disjuncts

in my humble opinion  

As we saw above, modal adjuncts are often simple adverbs or adverb phrases such as:
    He's definitely her brother
    That's probably her brother
    That's very likely her brother

They come in two main flavours:
Amplifiers or emphasisers: definitely, certainly etc.
Downtoners or softeners: possibly, conceivably, apparently etc.
and a few are limiters which constrain the nature of the utterance:
    Currently, this must be the case
    That was always true formerly

Prepositional phrases, such as, without any doubt, in all likelihood, at the moment, in principle etc. perform the same functions.

As we also saw above under evidentiality, disjuncts, especially of attitude or content, are frequently used.  Style disjuncts, too may signal truthfulness or doubt as in, e.g.:
    In my opinion, that's her brother
(style disjunct restricting the way the speaker wants to be understood)
    Truthfully, I have no idea where I put it
(style disjunct of manner expressing the way the speaker wants to be understood and implying it is true)
    Arguably, this is a problem
    Obviously, that's her brother
(both attitude or content disjuncts referring to the truthfulness of the proposition)

There is a guide on this site for more on adverbials, linked in the list at the end.


Personal opinion

I suspect she's lying  

In addition to the attitudinal or content disjuncts noted above, there are two further ways to express epistemic modality to consider.  In the list above, they appear as:

Attributive clauses
The examples above were:
    I'm quite sure
that's her brother
    I'm almost certain
that's her brother

Attributes, whether modified adverbially or not, can be expressed in the whole range:
High perceived likelihood:
    I am convinced that's (not) her brother
    I feel absolutely sure that's her brother

    She appears certain that that's her brother
Mid-level perceived likelihood:
    I am partially convinced that's her brother
    I am a bit doubtful about whether it's her brother or not

Low-level perceived likelihood:
    I am very doubtful that's her brother
    I feel quite sure that's not her brother

The most common copular verbs are appear and seem (for other people's views), feel and be (for personal views) but others such as grow, come and become are possible as in, e.g.:
    I have come to the view that he doesn't like me
    I have grown to understand the truth of the matter
    She has become convinced of the validity

These attributive expressions can be combined with modal auxiliaries as in, e.g.,
    I am sure that must be her brother
    I am doubtful that could be her brother

to provide quite subtle shades of viewpoint expression.
Verbs of mental processes
The examples above were:
    I think that's her brother
    I doubt that's her brother
A range of verbs are possible both in the positive and the negative.  For example:
    I (don't) think that's going to happen
    I (don't) doubt that's the truth
    I suspect that's her brother
    I (don't) believe that's her brother
An added complication here is that English speakers often opt for what is known as transferred negation (see below).


Epistemic modality is widely used in formal writing, especially writing in English for Academic Purposes because expression which seems overly assertive and dogmatic is generally avoided.
For example:
Instead of:
    It is clear that ...
writers often prefer something like:
    It may be successfully argued that ...
Academic writing makes full use of modal auxiliary verbs, modal adjectives, modal nouns, adverbs and prepositional phrases in an effort to sound reasonable and tentative rather than assertive and over-confident.
Other examples are:
    The discrepancy could be the result of ...
    It might be argued that ...
    It seems to be the case that ...
    This tends to be the result of ...
    It may, quite arguably, be the case that ...
    It seems, as far as we can discover, to be the result of ...
The guide on this site to the use of hedging and cautious language in EAP is linked in the list of related guides at the end.  It contains many more examples (including the six above) of how epistemic modality expression is toned down to remain appropriately tentative.

cats eyes

A peculiarity of English

When negating clauses containing mental process verbs, most languages will put the negation where it belongs, i.e., with the verb that is being negated.
For example:
    I think that he hasn't done it yet
    I expect he won't come
    I imagine she has no money

    I think she's not very friendly
In all these cases, we have a verb signalling belief followed by a subordinate clause which is negated in some way.

English, bizarrely, often chooses to negate the main clause and leave the subordinate clause positive.  This is called transferred negation.  It only occurs with verbs signalling belief or assumption (i.e., epistemic modality) including, but not limited to
    believe, suppose, guess, fancy, imagine, reckon, expect
For the three sentences above, for example, English speakers would naturally select:
    I don't think he's done it yet
    I don't expect he will come
    I don't imagine she has any money
    I don't think she's very friendly
The illogicality of transferred negation is revealed when a questions tag is included so we get, for example:
    I don't think he's done it yet, has he?
instead of the expected, do I?

To make matters worse, not all such verbs allow this transfer.  For example, assume and presume do not work this way:
    I assume you haven't paid [assumption = you haven't paid]
is not the same as
    I don't assume you've paid [no assumption made]
The verb hope is also odd because it will not allow the transfer:
    I don't hope it rains [= I do not hope for rain but I may expect rain]
is not the equivalent of
    I hope it doesn't rain [= I am hoping for no rain]

See the guide to negation in English for more, linked from the list below.  There is also a PDF file with a list of verbs which do and do not allow transferred negation, available here.

Related guides:
non-modal-verb modality covers some of the above and extends it to include epistemic and other forms of modality
types of modality for an overview of the area
dynamic modality which follows a similar format to this one
deontic modality which follows a similar format to this one
multiple modalities for a guide which considers how different types of modality may be combined in single utterances
modality and aspect for more on the use of modal auxiliary forms in complex tenses
the modality map for more choices
negation to find out more about transferred negation
ambiguity for a guide which considers the polysemous nature of many modal auxiliary verbs and the ambiguity which can arise
hedging in EAP in academic writing epistemic modality is widely used to write cautiously
adverbials for more on adjuncts and disjuncts (and much else)

Aikhenvald, AY, 2004, Evidentiality, Oxford: Oxford University Press
Palmer, FR, 2001, Mood and Modality, 2nd edition, Cambridge: Cambridge University Press