Can someone shout out some philosophical discussions dealing with inverse relationships?

Question

Take this quote for instance," Volunteers need both selfish and selfless motives to sustain their interest"(Natalie de Combray). I found it while looking at the definition for selfless.

Answer 1

I think people gain happiness generally through both internal and external rewards.  We might do something because WE enjoy it, but if it serves no greater purpose, our enjoyment is limited.  We might do something because it helps other people, but if we take no pleasure from it, then it feels as if we are giving away and receiving nothing in return, which people can do only for so long.  The best scenario is both - we enjoy what we are doing, and it is of benefit to others.  

(You might re-post this question tomorrow.  A glitch is preventing questions from appearing in their individual categories right now, so you may not get many answers).

Answer 2

Time and rate of motion.