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Section 6.16

Sequence of Tenses

Choose the tenses of your verbs accurately to express the timing or sequence ofevents that you are describing. Often, the particular sequence of events thatyou are describing will require you to use several different verb tenses withina single sentence or paragraph. Although it is appropriate to vary your verbtenses in accordance with the actual timing of the events, you should avoid shifting tenses unnecessarily.

Pay special attention to how you express the sequence of tenses when describingthe timing of events or when paraphrasing ideas.

Sequence of Tenses and Timing of Events

To emphasize that an event occurred or was completed before another event, usea form of the perfect auxiliary have.


Past Perfect

By 150 B.C., the Greeks had accuratelydetermined the shape and dimensions of the Earth and thedistance of the Moon, but had not managedto probe very far beyond that.

--Isaac Asimov, The Universe

Infinitive

The reaction appears to have finished already.


To express that an event in a participial phraseoccurred at the same time as the event described in the main clause, use a presentparticiple.


Arising from the complex flow and interaction ofinformation, life is a dynamic process.

--Kai Wu, "Artificial Life," SciTech Magazine (modified)


To emphasize that an event in a participial phrase occurred before the eventdescribed in the main clause, use a perfect auxiliary and a past participle.


Having examined the peculiar data carefully, theinvestigators concluded that the equipment was faulty.

When writing formal documents, use the simple past tenseto describe habitual actions. Although the modalwould is often used to express past tense habitual actions, its use isgenerally restricted to spoken and informal contexts.


Weak

Before the development of anesthesia techniques, surgeons wouldprepare their patients for surgery by getting them drunk.

Improved

Before the development of anesthesia techniques, surgeonsprepared their patients for surgery by getting themdrunk.


Sequence of Tenses and Paraphrasing

When paraphrasing a written idea, introduce the paraphrase with a present tense verb (e.g., writes) and do notchange the original verb tenses of the idea.


In his book The Universe, Isaac Asimov seeksto trace the steps by which mankind's grasp of the universewidened and deepened.

When paraphrasing an ongoing or future spoken idea, introduce the paraphrase witha present or future tense verb (e.g., says)and do not change the original verb tenses of the idea.


Unacceptable

At tomorrow's meeting, she will officiallyannounce she will be chosen yesterday tolead the government research project.

Acceptable

At tomorrow's meeting, she will officiallyannounce she was chosen yesterday to leadthe government research project.


When paraphrasing a previously spoken idea, introduce the paraphrase with a pasttense verb (e.g., said) and change the verb tenses of the idea to matchthe tense of that verb.


Unacceptable

The engineer informed us that she is notable to field-test the device yesterday because it israining.

Acceptable

The engineer informed us that she was notable to field-test the device yesterday because it wasraining.


If a previously spoken idea is a general fact that is always true or concerns afuture event that has not yet occurred, you can either maintain the original verbtenses of the idea or shift them to past tense to match the tense of the verb youused to introduce the idea. Maintaining the original tense emphasizes thecontinuing validity of the idea, whereas shifting the verb tenses emphasizes thenarrative quality of the paraphrase.


Acceptable

Von Neumann postulated that an automaton will need atleast six elements: a computer, a sensor, a manipulator, a cutter, a fuser, and"girders" from which the automaton will be built and whichencodes instructions to act as "memory." [continuingvalidity emphasized]

Acceptable

Von Neumann postulated that an automaton would need atleast six elements: a computer, a sensor, a manipulator, a cutter, a fuser, and"girders" from which the automaton would be built and whichwould encode instructions to act as "memory." [narrative quality emphasized]

--Kai Wu, "Artificial Life," SciTech Magazine (modified)


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