Cambridge Grammar of English Hardback with cd-rom a comprehensive Guide

Modality and tense-aspect

146a

Will

is used to make confident predictions or to assert known or accepted facts:

Represented as a value between zero and one, X 

will approach unity in

perfectly flat and open terrain, whereas locations with obstructions such as

buildings and trees 

will cause X to become proportionally less (Oke, 1992). 

[pathology lecture]

Right. Red blood cells leaving the capillaries and then entering the tissues.

They

’ll break down there and haemoglobin will be released and the tissue will

turn black and eventually 

will go.

Must

is used to make confident predictions or conclusions:

Such changes 

must be due to changes in motivational organization of social

behaviour.

Must

is also used in boosted directives to the reader/listener to pay attention to

particular points:

We 

must remember, however, that migrants may not need information about

more than one destination.

(compare the weaker: We should remember, however, …)

It is useful to try to apply these general stages when considering any piece of

worked stone. As always, they are meant to help us understand the processes

and as such are merely an intellectual framework. Therefore one

must not

apply them too rigidly.

The unmodified simple forms of verb tenses are used to make non-hedged

assertions:

Attachment, then, 

results in close and prolonged proximity of bacterial

digestive enzymes with the substrate.

(compare the hedged: Attachment, then, may/can/could/might/should result

in close and prolonged proximity of bacterial digestive enzymes with the

substrate.)