Well...perhaps not...but at least I could begin with what I consider to be the most fundamental question of life: What is man for? As an Orthodox Christian, I have a venerable tradition to draw from, which provides context and content to life...but many of the answers that one can find (in patristic writings, liturgical texts, hagiography, and so on) offer answers that require a certain amount of interpretation. Of course, one could answer that man is made to be united to God...and this is, of course, ultimately true.
But how does this work? Most specifically, what does this mean for me as a Christian living in the world? Am I to attend solely to myself (as if this were even possible) and not worry about others? Of course, one might answer, yes, in fact, this is exactly what we are called to...look at how most of the Saints separated themselves for years, so as to acquire the grace of God and thereby be able to provide other people with a vision of a life transfigured...a life truly "in Christ." And in one respect, this is true.
At the same time, for better or for worse, I spend most of my life doing other things...mostly neutral perhaps, sometimes more virtuous, sometimes less so. Although the virtuous and the sinful things I do have the greatest effect on me spiritually (or so one would think), they tend to take up the least amount of time...sadly, I have not yet been granted unceasing prayer. Most of my time is spent with the neutral aspects of my life: sleeping, eating, working, recreation, and so on. Certainly all of these neutral things may be done to the glory of God, but are they? And how to make sure that they continue to be glorifying?
Finally (for now, this post has rambled on long enough), what is the hierarchy of values that inform one's life (and thereby provide some kind of criteria for evaluating the answer to the original question regarding the purpose of man's life on earth)? Certainly, belief in and a life dedicated to Christ and His Church inform all other things. What is second, though? My guess is that for one called to monastic life, it is his/her monastic vocation...and for one called to marriage, it is his/her vocation as a husband/wife/father/mother. Third? This is probably where most of the dialogue belongs...is my own salvation third in the hierarchy of values? Is the salvation of my brother/sister completely tied to my own salvation? Would this place his/her salvation on the same level as my own as regards my personal responsibility and the hierarchy of values? Christ's words and the patristic tradition would seem to support this..."My brother is my life" as Saint Silouan says. If this is the case, what does this mean for me? for how I order my life? for the decisions I make? for the way I spend my time?