It is an important thing to do or to be done? [duplicate]

Which one is correct? Can i use them interchangably and is there a common rule for such constructions? Thanks in advance.

Solution 1:

It is an important thing to do contains an example of what The Cambridge Grammar Of The English Language (CGEL, p1255) calls a 'hollow non-finite clause:

In its general introduction to the topic, the CGEL gives these examples (among others):

• The problem took her only a few minutes to solve.
• That he would do such a thing is hard to believe.
• You won't find these kids easy to teach.

According to the CGEL "there are six constructions where hollow to-infinitivals are required or permitted". The second of these constructions are those that "are licensed by an attributive adjective". This construction type matches the sentence in question It is an important thing to do.

Among the examples given are:

• It's a difficult book to understand.
• That wasn't a very sensible remark to make.
• This was a surprising decision for them to take.

The last of these provides the pattern for an alternative to the OP's sentence. Namely the inclusion of the subject:

• It is an important thing to for you (me/him, etc.) to do.

The CGEL does not explicitly rule out the passive in such constructions. But using the passive here makes the sentences more complex than they need to be. And it makes them sound unnatural to me as a native English speaker.

Addendum: A similar question was asked about the first of CGEL's hollow to-infinitivals ('as a complement to predicative adjectives and nouns'). The answer contains a link to Wikipedia's interesting grammatical feature called tough movement.

To explain or to be explained