Unit 10bc Book

So far, you have had a chance to read lots of sad stories about electrical hazards. Most of them have one thing in common: the investigation usually reveals the possible causes of the incident, criticizing some faulty procedures. This criticism may then be followed by some recommendations of what should be done to prevent a similar accident in the future. Take this sentence from one of the stories, for example:

• There were exposed conductors in the welding machine’s cables.

Imagine being in the shoes of the investigating officer. If there were no surviving witnesses and no CCTV cameras around, you cannot be a hundred percent sure about this statement prior to the end of the investigation. So before finishing the investigation, you would probably speculate like this:

• It is probable/possible that there were exposed conductors in the welding machine’s cables.

or, alternatively, you would say:

• There may/might/could have been exposed conductors in the welding machine’s cables.

That is: may or might or could for showing uncertainty and have been for showing the fact that you are speculating about the past, not the present.

How would that sentence change if there had been a CCTV camera around during the incident and if the investigation was completed?

Well, you would be more certain and you would say something like:

• It is certain that there were exposed conductors in the welding machine’s cables.

or, alternatively, you would say:

• There must/have to have been exposed conductors in the welding machine’s cables.

That is: must or have to for showing certainty and have been for showing the fact that you are speculating about the past, not the present.

You can also express the same meaning by using a negative sentence with can´t/couldn´t:

• The conductors can´t/couldn´t have been insulated in the welding machine´s cables (otherwise there hadn´t been any accident).

So, you would mean that this is not possible (or that this is impossible).

You can also use a similar pattern to show criticism and recommendation:

• All the conductors in the welding machine´s cables should have been insulated.

Which means the same as:

• All the conductors in the welding machine´s cables ought to have been insulated.

That is: by this sentence, you criticize something that should have been done in the past, but it wasn´t.

If this explanation is not enough for you and you prefer general English context, study this grammar overview. Then practise this grammar point in this vocabulary task and then here and here.