Data: “Since her death, I’ve been asked several times to define “how well” I knew Lt. Aster. And I heard you ask Wesley on the bridge, “how well” he knew Jeremy. Does the question of…familiarity, have some bearing on death?”
Riker: "Just human nature, Data."
Data: ”Human nature, sir?”
Riker: “We feel a loss more intensely when it’s a friend.”
Data: “Hm. But should not the feelings run just as deep regardless of who has died?”
Riker: “Maybe they should, Data. Maybe if we felt any loss as keenly as we felt the death of one close to us, human history would be a lot less bloody.”
-The Bonding, S03E05