Not an easy question. I Think that before such a question can be answered other questions have to be resolved like Who and what is Man and what is the Essence of Man (human life) and the purpose for ones existence. As our quest to understand this continues we find that we are born, live and die on a very small speck of rock hurtling through space at over a million miles an hour coming from nowhere and going to nowhere.
For a foundationlal thought I would say that our capacity to Reason is the Essence and self determination is the purpose, With that in mind then the US Constitution becomes an essential starting point. The problem is, as we see today human greed and the desire to rule over others (socialism and totalitarian rule) destroys the individual and individual freedom.
Sadly, I think, we have a better chance of destroying the planet then achieving our potential, as reasoning beings, as we shun such responsibility..