Defining Sin

Driving home from dinner last night, Michele asked me if I had ever defined sin in my sermon, because I talked quite a bit about it, but she wasn't sure I actually defined it.  I was actually pretty sure I had, and was about to demonstrate some sin, by getting angry, frustrated or whatever that she didn't get it. My oh, so clever sermon states that sin is rooted in thinking that we know better than God.  I still think it's a pretty good definition, going back to the aboriginal catastrophe as it is envisioned in Genesis, the "first" sin is precipitated by the desire to be like or be perhaps even better than God.
I worked out from there is a wonderful and elegant process, in which I considered whole rafts of different sorts of sin, which can all be reduced to violating or at least ignoring God's good purposes and/or despising the Love of God.  Sin is bad for you, it carries unhealthy consequences in physical, emotional and spiritual reality.  God, as Creator, knows how we work and thus has prescribed some rules and boundaries, "for our own good."
The rules are not always absolute, and to some extent, they are intended to be broken in certain cases and perhaps entirely abolished in other cases.  My definition of sin rests on what I would like to think is a non-legalistic foundation.  My assumption is that all of the rules that God actually makes, as compared to the ones that humans invent or extrapolate from God's Law, are entirely good.  Unfortunately they are also rather broad and in need of constant evaluation and interpretation, and thus come the lawyers, and the ever increasing complexity of case law.  Case in point: "Thou shall not kill," which in most systems is recognized to be an entirely untenable edict.  Let's face it, between criminals and other enemies of the common good, there's always some killing that's got to be done in order to preserve the security of the people.  So we parse the rule, "thou shall not kill, but actually that really means murder, so, you know, accidents, executions and stuff that happens in war really doesn't count."
But in actual experience, those sort of killing are also damaging to us, I mean to us as a society and also to the ones who do the killing.  You cannot kill another human being without consequence, even if it is "justified."  Soldiers often experience horrible guilt and post traumatic stress from the real experience of taking lives.  Even if they are entirely sure that their actions were in the defense of the common good, even if they are rigorously moral about doing their duty, there is still a price to be paid for doing something that God has made to "feel" wrong.
Michele's objection to my definition of sin was that she didn't agree with the premise that people who sin, "think they know better than God." My counter to that is that they don't actually plan to violate God's will, they just do because they put their own desires in front of what their conscience and the very fiber of their spirit tells them is wrong.  I feel that my definition holds whether you believe in God or not, and does not at all depend on your private moral landscape.
It is based on the simple observation of consequences, and the fact that almost everything we do has consequences, and left with only that information, we can indeed construct a basic idea of right and wrong.  "Right," or "righteous" things have good consequences, they increase our ability to enjoy life and to show the love of God to our communities and our world.  Sins have negative consequences, but are also masters of disguise, and experts at self-justification.  From the most pervasive and fundamental sins of jealousy and pride, to the final and "unforgivable" sin of not forgiving, we always have a ton of reasons whey we just can't repent and turn away.
And so, until we trust that God knows what is best for us, and learn to follow the path of radical forgiveness that Jesus has shown us, we are always, in some way, in rebellion against what God  has told us is best, and thus, implicitly, we are demonstrating our belief that we know better than God.
Indeed,it is not always that we consciously "think" we know better than God, but we demonstrate our derision for the goodness of creation whenever we sin, big, little or somewhere in between, and thus we are chained to our own guilt, because we never recognize that it's there.