Contrasts

CONCEPTUAL CONTRASTS The conceptual contrast between the present perfect aspect and the specific past can be shown diagrammatically, together with the compatibility principle with respect to appropriate adverbs. Aspect is shown as an unbroken extension of time from the past to the present, whereas the specific past is shown as segmented into distinct intervals. Compatibility of present perfect aspect with adverbs of duration Compatibility of past simple with adverbs of specific past time The meaning of continuous aspect is more difficult to define comprehensively, and particularly in the present tense has a wide range of meanings. We can, however, identify certain typical features which are in some degree present in these various uses. The continuous aspect is also known as "progressive" aspect, and this refers to one of the characteristic uses of the continuous form, which is to indicate that an action is in some sense progressing. This conveys also the feature of incompleteness, which is another typical semantic component of continuous aspect. The other principle notions which typically characterise the meaning of the continuous are the features *duration and momentariness*. We saw earlier that the past form of both the perfect and continuous aspects had the function of relating an event to the occurrence of another event. Whereas the past perfect indicates that an event occurred before another, the past continuous indicates an event occurring simultaneously with another. Both these uses contrast with the past simple tense.
e.g.	The train had already left when we arrived.
	They were eating dinner when we arrived.
A similar function may occur in the present continuous:-
e.g.	She's always smoking whenever I see her.
This however signifies an habitual aspect rather than momentary duration, and this is also one of the common functions of the present continuous.
e.g.	I'm writing a 100,000 word thesis.
	We're living in Sheffield.
This contrasts with the use of the present simple similarly to express habitual aspect, which we saw earlier is one of the typical uses of the present simple tense.
e.g.	I live in Sheffield.
	He works at the university.
There is perhaps a contrast in that the use of the present continuous to express habitual meaning suggests that some point of completion is envisaged, whereas the present simple suggests more permanence. However, this difference is not always clear.
e.g.	He's working in a bank.
	He works in a bank.
Generally, however, the present continuous tends to convey a suggestion of impermanence even where habitual meaning is expressed. The continuous aspect also contrasts with the simple tense in other ways. Like the ohter tenses we have discussed, the principle of compatibility with time adjuncts applies. Consider the following:- e.g. I'm writing it now. * I write it now. Particularly with processes which are dynamic activities, and which themselves inherently presuppose duration, the continuous aspect tends to be more appropriate, as in the above example. In such cases, the present simple seems to be incompatible with an adjunct such as "now", and would thus be inappropriate. If habitual meaning is expressed, however, the present simple is acceptable. e.g. I write something every day. If the continuous aspect tends to be associated with dynamic processes, which are typically transient, the reverse is the case with respect to processes which describe states or qualities which are regarded as permanent or unchanging.
e.g.	She's got eyes of blue and that's my weakness now.
	* She's having eyes of blue.
The present continuous, like the present simple, is also compatible with time adverbials indicating future. It is often used to indicate intentions, plans and arrangements.
e.g.	They're having a party next week.
	I'm seeing him tomorrow.
*Combination of perfect* and continuous aspects** Both perfect and continuous aspects may occur in the same verbal group. To see how this takes place we must consider how the structure of the secondary tenses is realised. The perfect tense is formed by the auxiliary verb HAVE + the "n" form of the main verb. If we use the symbol "h" to represent "have", the structure may be shown as follows, where the brackets "[]" show that the morpheme to the left of the brackets is attached to the element which they enclose:-
perfect --> f[h] + n[v]
The structure of the continuous tense is formed by the auxiliary verb BE + the "ing" form of the main verb, and can similarly be shown as follows:-
continuous --> f[be] + ing[v]
When the two aspects are combined, the perfect auxiliary HAVE always precedes the continuous auxiliary BE. Therefore only the "h" auxiliary is finite. The "n" morpheme is thus attached to the latter, and the "ing" morpheme which follows the auxiliary BE is attached to the main verb in final position. The structure is as follows:-
perfect continuous --> f[h] + n[be] + ing[v]
The logical sequence of the tenses is thus:-
PERFECT + CONTINUOUS + MAIN VERB
This can also be shown in the form of a structural tree with respect to an example:-