The apostle had himself instructed the Thessalonians believers while he was with them, and yet now he is concerned lest they should be ignorant. It is quite likely they have not got these things clearly in their minds, for the apostle was not with them for long.
It is like today. When celebrities or well-known people die, you hear of the funerals reported in the news, and there is all the talk about him or her being up there looking down. It is no certain hope. That is just something that you say at a funeral, when it is a funeral in which the Lord is not believed in and trusted. Your natural instinct driven by sentiment tells you that somehow the person is still there and still alive, but you have not really got a hope. You have not got any hard information; it does not take any shape or form. It is not only an uncertain hope, it is an uninformed hope, it is an unauthoritative hope.
What did the Greeks believe about the afterlife? The idolatrous religion of the Greeks did believe in a kind of life after death, but it was a dismal thing. The soul just went in to the murky depths of nothing, and there was no relating or knowing anyone else. We must sleep an endless night, said a Greek poet. So they wailed and mourned, and funerals were tortuous and stretched out affairs, going over days and sometimes weeks.