Paul is seeking in this passage to both encourage and call on his listeners to encourage others to be hopeful about those who have died in Christ. It is absolutely not the end for them. They can and must remain hopeful. But how? Paul gives clear direction. They (and we!) remain hopeful by looking to Jesus (the One who died but didn’t stay dead), listening to what Jesus says on this matter, and by going and comforting others with these truths. 
(1 Thess. 4:13-18)