Deontic modality conveys meanings that are related to the signer’s attitude towards an event, expressing its necessity or possibility. Some of these deontic meanings are obligation/necessity, recommendation, ability, permission, and intention/volition.
In LSC, obligation and necessity are primarily expressed through the signs must-0 and must-5. Both signs are articulated with brow furrow and head nod.
a) must-0
b) must-5
These signs seem to be synonyms since they can appear in the same contexts. However, there is a difference between them based on degree. The sign must-5 seems to be more emphatic than the sign must-0. In other words, when the sign must-5 is used there is no way to avoid the obligation expressed in the proposition. Moreover, the two signs can combine in the same sentence to emphasize the modality [see SYNTAX 2.3.1.3 for further discussion on this issue].
a) woman child vegetables eat must-5.
‘The girl must eat vegetables.’
b) woman child vegetables eat must-0.
‘The girl must eat vegetables.’
c) paper sign each_one+++ must-0.
‘(You) must sign each one of the pages.’
d) paper sign each_one+++ must-5.
‘(You) must sign each one of the pages.’
Regarding the negation of these modal elements, there are some negative forms that involve cliticization of the negative particle. In example (a) the modal must-0^not is expressing obligation, and it is coarticulated with raised eyebrows and a head nod. In example (b) the modal need^not is expressing necessity, and it is coarticulated with furrowed eyebrows plus a head nod.
re, hn
a) paper sign each_one+++ must-0^not.
‘You don’t have to sign each one of the pages.’
fe, hn
b) paper sign each_one+++ need^not.
‘(You) don’t need to sign each one of the pages.’
Recommendation in LSC is expressed by the sign should-0, which is a combination of the manual sign must-0 with a different non-manual marking: raised eyebrows, eyes wide open, and a head nod. Also, the movement in should-0 is laxer in comparison to must-0, as can be observed in the minimal pairs (a-b), and (c-d) below.
a) should-0
b) should-0 study more.
‘You should study more.’
c) must-0 study more.
‘You should study more.’
d) study more must-0.
‘You should study more.’
e) study more should-0.
‘You should study more.’
Ability can be expressed with the signs can and be_able as illustrated in the examples below.
a) can
b) be_able
c) ix1 sea dive one minute can.
‘I can hold a minute under water.’
d) ix1 sea dive one minute be_able.
‘I am able to hold a minute under water.’
Negation of these modals is realized by an irregular form: cannot (a). It can also be expressed with the antonym impossible (b), and/or with both elements combined (c), yielding a more emphatic interpretation.
a) ix1 sea dive one minute impossible.
‘I cannot under any circumstances hold a minute under water.’
b) ix1 sea dive one minute cannot.
‘I cannot hold a minute under water.’
c) ix1 sea dive one minute cannot impossible.
‘I cannot under any circumstances hold a minute under water.’
Permission in LSC is expressed through the sign allow. In many languages the verb ‘can’ is also used in order to express permission, in LSC, however, this verb only expresses ability.
a) allow
b) out playground sign allow.
‘It is allowed to sign in the playground.’
Negation in this type of modal is realized with the particle not after the modal marker.
playground out sign allow not.
‘It is not allowed to sign in the playground.’
Intention and/or volition are mainly expressed with the sign want as shown below.
a) want
b) want ice-cream.
‘(I) want ice-cream.’
c) ice-cream want.
‘(I) want ice-cream.’
Negation with want is always realized through cliticization with the negative particle not placed after the modal verb.
a) want^not
b) ice-cream want^not.
‘(I) do not want ice-cream.’