- The police arrested a man.
- The police have arrested a man.
I don't know the difference between these two sentences. Could someone please explain?
I don't know the difference between these two sentences. Could someone please explain?
Would it be much simpler to say that the latter,"The police have arrested a man," implies its a current event from the recent past. The former, "The police arrested a man," refers to an event that took place anytime in the past.
The choice of perfect or past is usually a free one, in the sense that a speaker can choose either possibility to refer to the same events.
The difference is not in the events described, or the times when they happened, but in how the speaker is choosing to portray the temporal relationships.
When we use the present perfect ("have arrested") we are positioning the event as having some relevance to the present. That relevance could have different meanings: it could be that the event was very recent; it could be that its effects are still current (eg if the man is still in custody). Or it could be one in a series of events which extends to the present time (eg "The police have arrested a man, but they couldn't find enough evidence to charge him, so they've released him, and they haven't found any other leads, even though it's been weeks")
In all these cases, we could use the simple past, in which case we are not positioning the event as related to the present.
If the arrest was recent, or he is still in custody, we are probably more likely to use the perfect; but we don't have to if we are not concerned to portray the event as related to the present. eg "What did the police do when they found him there? They arrested him", even if this has only just happened.