When we learn English verbs, we usually spend a lot of time remembering when to use a certain tense A, and then when to use another tense B. However, few of us pay attention to when we should not use a tense A or a tense B. When we see “I’m loving you,” or “I have preferred this job” (note that it is different from “I would have preferred this job“), we say we should probably use the present simple in the first sentence, and the past simple in the second, instead of the present continuous and the past perfect respectively. But why not?
If we consider the problem more carefully, we will realize that it is not just that the present continuous “am loving” and the present perfect “have preferred” are inappropriate in these particular sentenses. Even if we try harder, we will still not be able to find the right situations in which these tense forms can be meaningfully used. The fact is, the respective tense forms practically do not exist for these verbs. Strangely, although there are more than a dozen different tense forms in English, not all tenses are applicable on all verbs. To understand why, we have to first understand some more properties of verbs.
Duration and Telicity
We normally define a verb as a word which describes a state or an action. Correspondingly, verbs are classified into two main types, stative verbs and dynamic verbs. However, using labels like “state” and “action” may sometimes be confusing. For example, is see a state or an action? Linguists have therefore developed other more effective means to characterize verbs, namely by specifying whether they have duration and whether they have an end-point.
Be it a state or an action, a verb describes an events that happens in time. If it happens in time, we can ask whether the event has an implied duration, meaning we can easily visualize the internal process of the event, or the event happens in such a blink of an eye that we normally cannot or do not talk about its internal process. In the first case, we call the verb durative. Verbs like walk, run, fix and kill are examples of durative verbs. In the second, we call it punctual, examples include realize, die, knock and blink.
On another dimension, we can ask whether an event has an end-point. In other words, does the verb imply a state in which the event is finished? If it does, like fix (the finished state can be a machine having been fixed, for example), kill (somebody dead), die (somebody dead, again) and realize (the state of knowing something previously unknown), it is called a telic verb. If it does not, like walk, run, knock and blink, it is called an atelic verb.
Based on these two criteria, we can refine our definitions of stative verbs and dynamic verbs, and further classify dynamic verbs into four subtypes, namely accomplishment verbs, achievement verbs, activity verbs and semelfactive verbs. These five types are referred as the lexical aspects of verbs.
Under this classification, stative verbs are verbs which describe static events (or actually, states). They are similar to durative verbs because states obvious last over a long time. However, they are different because we do not talk of the internal temporal structure, or the internal process of a state. They also have no implied end-point. The copular be is a good example of stative verbs. When I say “I am Chinese,” it certainly holds true over a long period of time. On the other hand, it does not imply the point when one day I will cease to be Chinese, it is hence atelic. Other examples are love, hate, like, prefer, mean, consist of, and so on and so forth.
If a verb is not a stative verb, it is called a dynamic verb. Dynamic verbs describe actions that occur over time.
Accomplishment verbs include words such as fix, kill and collapse. They have both internal temporal structure and a natural end-point.
Achievement verbs include words such as realize, die and forget. Since one either has realized something, or he hasn’t, there does not exist such a state when one is “realizing” something. Achievement verbs are therefore said to be punctual. They also have an implied end-point.
Activity verbs are durative and atelic. They include verbs like walk, run, see, drive, read and so on. They are similar to stative verbs, but differ from them in that activity verbs have a dynamic internal process whereas stative verbs do not. In other words, stative verbs involve no change over time, they are merely static descriptions.
Semelfactive verbs express punctual actions that last only a short time and do not have any distinguishable internal structure. Unlike achievement verbs, though, they do not imply an finished state. Examples of semelfactives include blink, knock and sneeze.
This could be quite abstract and confusing at first glance, but if it seems neat to you so far, the next step is to realize that we normally do not speak of the lexical aspect of a verb per se, but that of an entire verbal phrase in a particular context. This is because the same verb used in different verbal phrases in different contexts can have different lexical aspects. Compare the following sentences:
1. I read before I go to bed.
2. I read a book before I go to bed.
In (1), read has no end-point, therefore it is an activity verb. In (2), though, read a book specifies an end-point, i.e. one book is finished. Therefore, in this case, read is an accomplishment verb. In short, there is no one-one correspondence between verbs and lexical aspects.
Lexical vs. Grammatical Aspects
We have gone all the length to learn what lexical aspects are, now we are ready to see how they are related to our original question.
You may have noticed that the two dimensions that we have discussed, namely duration and telicity, closely relate to the progressive (continuous) and perfect aspects in compound tense forms in English. Recall that an aspect provides information on the temporal structure of an event (see What’s in a verb?), so we can say the progressive aspect describes an event which has a temporal duration (thus durative) and the perfect aspect describes an event which has a terminal point (thus telic).
In other words, lexical aspects are no different than progressive and perfect aspects, which can also be called grammatical aspects. They essentially encode the same type of information, only that whereas grammatical aspects encode it by means of syntax and morphology, lexical aspects plant the information inside individual words.
Once this is made clear, it should then be evident why stative verbs such as love, hate, and punctual verbs such as realize, die and forget cannot be in the progressive aspect, and why atelic verbs such as prefer, mean and consist of cannot be in the perfect aspect. Taking the sentence “I’m loving it” as an example, it is because the gramamtical aspect, i.e. the progressive aspect, is incompatible with the lexical aspect of the verb, i.e. stative, which is atelic.
Apparently, however, there are many exceptions to this. For example, consider the following examples:
3. Who is knocking at the door?
4. I have driven (before).
5. I have (just) run a marathon.
First, we should understand that the “continuous tense” in English does not only represent the progressive aspect. In (3), “is knocking” does not express a prolonged, unfinished instance of “knocking”, but a series of repeated “knockings”. Linguists call it the frequentative aspect.
Similarly, the “perfect tense” in English does not merely represent the perfect aspect. In (4), the sentence focuses neither on the terminal state of the event nor on the fact that it has finished. Instead, it only recounts an experience. It is called the experiential aspect.
Since punctuality and atelicity only clash with the progressive aspect and the perfect aspect respectively, the two sentences above are thus grammatical.
In (5), we have to once again remind ourselves that there is no one-one correspondence between verbs and lexical aspects. Although the verb “run” alone is normally an activity verb, the phrase “run a marathon” specifies an end-point, and is an accomplishment verb, which is telic. Therefore, it can be used in the perfect tense.