Imagination is a key.
Longing can be pleasurable, but the deepest longing with which we have experience is at times of death. Then the portals are opened wide as we pine for what has been lost and we hope for the best. Here we meet a gate leading to the moral dimensions of natural philosophy. I'll be brief and leave the preaching to others. We stand at the gate with a key, but the key will not work if our imagination is false and heartless.