Ordinary referential it has some referent. As a result, it can be replaced by a more complex description of that referent, and it can function (at least marginally) as a short answer to a question. These facts are illustrated in (1) and (2).
|(1)||a.||It bit the zebu.|
|b.||The tsetse fly bit the zebu.|
|(2)||a.||What bit the zebu?|
Referential it can also receive stress in longer answers like (3).
|(3)||a.||What bit the zebu?|
|b.||(pointing) 'It did.|
By contrast, expletive it doesn't refer, so it can't be replaced, as shown in (4).1
|(4)||a.||It seems that the manuscript has been found.|
|b.||*||The fact seems that the manuscript has been found.|
Expletive it cannot function as the short answer to a question; in fact, as (5) shows, even the question designed to elicit the short answer is impossible.
|(5)||a.||*||What seems that the manuscript has been found?|
Finally, expletive it is unable to receive stress in contexts where that is possible for referential it.
|(6)||a.||*||What seems that the manuscript has been found?|
Ordinary adverbial there has a locative meaning, so that the adjuncts (right) here and (over) there render (7a) and (7b) contradictory and redundant, respectively. It is possible to stress ordinary there.
|(7)||a.||#||There comes the train (right) here.|
|b.||There comes the train (over) there.|
Expletive there, on the other hand, has no such locative meaning, and so both sentences in (8) are completely acceptable. In contrast to ordinary there, expletive there can never receive stress.
|(8)||a.||There is a clean shirt (right) here.|
|b.||There is a clean shirt (over) there.|
|(i)||a.||It is evident that the manuscript has been found.|
|b.||✓||The fact is evident that the manuscript has been found.|
The reason is that (i.b) need not be structurally parallel to (3b). Rather, it can be derived from (ii) by rightward movement of the that clause.
|(ii)||✓||The fact that the manuscript has been found is evident.|
Such rightward movement is independently motivated by pairs of sentences as in (iii).
|(iii)||a.||They will report the fact [ that he was indicted ] tomorrow.|
|b.||They will report the fact tomorrow [ that he was indicted ] .|
A corresponding derivation is not possible for (3b) because the counterpart to (iii.a), given in (iv), is ungrammatical.
|(iv)||*||The fact that the manuscript has been found seems.|