Perfective versus imperfective

Many statements can be phrased either with perfective -s or with imperfective is -ing. A commentary on a domestic scene could include any of:

(9pe) John washes up

(9im) John is washing up

(10pe) Mary does the ironing

(10im) Mary is doing the ironing

A perfective sentence treats an activity as a unit, without regard for its internal composition. It may have a duration in time but this is not taken into account in the perfective statement. In contrast, an imperfective statement refers to the activity as spanning a period of time.

A perfective can locate its event as included within the time span of an event described by an imperfective, as in both of (again from commentary on a domestic situation):

(11) John washes up while Mary is doing the ironing

(12) Mary does the ironing while John is washing up

In (11), the event of John washing up (here treated as a unit of activity by choice of perfective) is shown to be included within the time span of Mary’s doing the ironing (marked as imperfective). This is reversed in (12).

However, the imperfective in English does not just focus on the time span and internal composition of an event. It also implies that the activity described is dynamic and evolving. Consider a perfective sentence with inanimate and animate subjects:

(13pe) The wall surrounds the city

(14pe) The army surrounds the city

These describe a continuing state, that the wall/army is all around the city. When imperfective is used the results are quite different:

(13im) *The wall is surrounding the city

(14im) The army is surrounding the city

Sentence (14im) describes a continuous and evolving process whereby the army gradually extends itself until it is all around the city. Sentence (13im) is unacceptable since—although it describes something which is extended in time (maybe for several hundred years)—there is no activity involved.

Consider also:

(15pe) I think [that you should go]

(15im) I’m thinking about [whether you should go]

Sentence (15pe) describes a formed opinion, a unit. In contrast, (15im) describes a continuous and dynamic process, weighing up the pros and cons of whether you should go.

The contrast between a normally invariable state, and some unusual activity which interrupts it, can also be shown by using perfective for the former and imperfective for the latter, in order to stress the change. For example:

(16) He normally drives a Volvo but this week he’s driving a Volkswagen (his Volvo is being repaired and the garage has lent him a Volkswagen for the week)

Whether or not an imperfective can be used may depend not on subject or verb but on the nature of a non-subject argument. One can say:

(17) John is having a series of injections

This is an extended dynamic process, with one injection after another. But it is infelicitous to say:

(18) John is having a lot of fruit in his orchard this year

Such a non-dynamic statement is limited to the perfective: John has a lot of fruit in his orchard this year.