In the last three lessons we have studied the auxiliaries used in
distinguishing the time of an action. We shall now study the auxiliaries
_can_, _may_, _must_, _ought_, _should_ and _would_, which enable us to
express other distinctions.
=CAN.=
=PRESENT TENSE.=
=Singular.= =Plural.=
1. I can, 1. We can,
2. Thou canst, 2. You can,
3. He can. 3. They can.
=PAST TENSE.=
=Singular.= =Plural.=
1. I could, 1. We could,
2. Thou couldst, 2. You could,
3. He could. 3. They could.
_Can_ is used to denote power or ability; as, I _can_ sing. He _could_
write very rapidly.
=MAY.=
=PRESENT TENSE.=
=Singular.= =Plural.=
1. I may, 1. We may,
2. Thou mayest, 2. You may,
3. He may. 3. They may.
=PAST TENSE.=
=Singular.= =Plural.=
1. I might, 1. We might,
2. Thou mightest, 2. You might,
3. He might. 3. They might.
_May_ is used to denote permission, possibility, or a wish; as, You
_may_ leave the room. He _might_ succeed again. _May_ you be there too.
_Could_ and _might_ are used sometimes in a conditional sense; as, They
_might_ stay here if we _could_ help them.
The phrases made by the auxiliaries _may_ and _can_ with the infinitive
of a verb are sometimes called _potential verb-phrases_, because they
express that an action is possible from the subject having power to
perform it.
=MUST and OUGHT.=
_Must_ has no other form. It is used to denote necessity or obligation;
as, I _must_ remain here.
_Ought_ is the old past of the verb _owe_. It is used to denote duty or
obligation; as, I _ought_ to help him.
The phrases made by the auxiliaries _must_ and _ought_, with the
infinitive of a verb, are sometimes called _obligative verb-phrases_,
because they imply _obligation_.
=SHOULD and WOULD.=
_Should_ and _would_ are the past tense forms of the auxiliaries _shall_
and _will_.
_Should_ and _would_ are especially used with the infinitive of a verb
to express a conditional statement; as, _I should do so_ if I had the
opportunity. _He would come_ if I asked him.
Since the phrases formed by _should_ and _would_ with the infinitive of
a verb imply a condition, they are called _conditional verb-phrases_.
1. _Should_ and _would_ are often used in expressing the condition
itself; as, _If he should be here_, they would know it.
2. They have sometimes their more independent meanings of _ought_ and
_be determined_; as, _I should go_, I know. _She would come_, no matter
what happened.