As Gill says, this is not a question about how death entered the world, as Paul describes in Romans 5:12, but it is about the gate through which all mortal beings must pass in their passage out of this world. Then we will know it by experience, but now we contemplate it at a distance. We know that such a gate exists and we know we have to go that way, but we remain ignorant of it in so many respects. We do not know when we will reach it, or what the circumstances will be – whether we will be surrounded by loved ones, or facing it alone; whether we will have to time to prepare or whether it will come suddenly and unexpectedly.
But more than the circumstances, we do not know the horrors of it, the terrible gloom and hopelessness that darkens its portals into the next world. We have not truly felt the terror of the endless hell that follows it, from which there is no escape and in which the soul is trapped forever. We have not seen that invincible confidence with which it closes on all who enter its gates and its vast experience at extinguishing all hope on those whom it swallows up. We have not felt the full force of its cruelty and tyranny, but from the land of the living we have as yet only heard a rumour concerning it.