Representing when, where, how and why

Representing why

page 4 of 5

Choosing between it is because and this is because

In general, this is because is used when referring back to an extended stretch of text such as a whole sentence.

In the following example, this is because is used because this refers back to the whole of the previous sentence:

We are just under one inch taller on getting up in the morning than we are on going to bed at night. This is because, during sleep, our spine no longer needs to support the weight of our body. Therefore, fluid passes into the discs between our vertebrae, causing them to swell. (Microconcord Corpus A)

However, there are exceptions to this general guideline. When referring back to a sentence that asks a direct question, it is because is preferred to this is because:

A:	Why are you always so tired?
B:	I think it's because I am not sleeping properly.

This is true even when a speaker or writer answers his or her own question:

Why has professional opinion hardened this way? Partly it is because of the growing conviction that the Prince's taste is indeed reactionary. (Microconcord Corpus A)

Another context in which it is because is often used is when it follows an if clause:

If US generic production seems more dynamic than that of the UK, it is because the economy is driven by difference as much as by repetition. (Microconcord Corpus B)

Here, the if-clause is used first to make a statement and then to ask why this should be the case - ie US generic production seems more dynamic than that of the UK. Why is this the case? It is because the economy is driven by difference as much as by repetition.

Finally, it is because also occurs in a special structure in which the it does not refer back to anything at all. This is an example of clefting, where a one-clause sentence is divided into two clauses:

Officials say it is because the two sides have different versions of what was decided at the previous negotiations that the ceasefire has broken down. (Microconcord Corpus A)

This is a common pattern where it is because is used. For further information about this pattern, see Using clefts and other structures to highlight information: it-cleft sentences (p 4).

 Introduction
 Using adverbial clauses beginning with because
 Choosing between because and it is because
 Choosing between it is because and this is because
 Using prepositional phrases