Sin. Such a small word but with huge ramifications and not really understood. There are various definitions of sin available for various purposes ranging from "missing the mark," to "breaking the Law." All the available definitions are appropriate in their contexts but all are themselves a bit off the mark.
If we are made to be cosmic, world-class, YHWH-image Lovers, then sin it seems at its core, is not-Love. In other words, anything that is done (intentionally) against the wellbeing of the other, against the building up, the glorifying of the other is not-Love or sin. To get a better picture of sin, we can look at its opposites in YHWH's revelation. We are told that the fruit of the Spirit is akin to a laundry list of good character attributes. We might start in Galatians 5, but that is not the only place we find the fruit of the Spirit. So then, patience, kindness, gentleness, even self-control are descriptors or evidence of the sort of Love we are after. Their opposites then are our first place to start looking for a definition of sin. Impatience, meanness, hardness, and yes, even lack of self control or dissipation are sin descriptors.
These things though are not sin because they some how violate a list of positive behaviors or attributes, but because they do not arise from a fully-formed Love. They are less than, incomplete, adulterated forms of real life that do not reveal an inward state of full Love. These then, the attributes or characteristics of not-Love are the basic, broadest, and most profound definitions and evidence of sin.
When we read of the Law of Christ, we are to understand "the law of Love," or "what Love demands, propels, causes." There is not a list of things in this law but rather an expectation of having been formed into the likeness of Jesus, the fullness of YHWH and therefore the very expression of divine Love. Murder isn't a sin because it has been listed as such but because it fails to reflect Love for the person killed. Adultery is not sin because it has been listed as such but because it fails to reflect Love for the person to whom we have already committed ourselves, or for the person with whom we commit adultery. Gossip, which shows up in the middle of more "serious" sins, is not sin because it is listed among those others, but because it fails to reflect Love for the person spoken about.
Lists of sins have their purpose and that is to remind us that our oft-too-human desires are not reflective of Love. Those lists those can never be exhaustive of all the ways - all the behaviors - we might reveal an imperfect Love for those around us. No, the measure of sin is that place from which it arises. Anything that arises from not-Love is sin.
This is good news and bad news. Good news that we aren't tied to lists of either good behaviors or bad behaviors by which we will be judged; we are truly freed from such things in absolute terms. The bad news - or perhaps the inconvenient news - is that we can't claim to be not-Loving just because we've managed to not kill someone. This, the problem the Pharisees and their buddies had. They thought that because they had the Law itself; that they even perhaps kept a lot of it, that they were therefore righteous, or sinless. What they had forgotten, much like the rest of us do from time to time, is that it isn't the finite thing we do or avoid that makes us righteous or sinful, but the place or character from which that behavior arises.
Not-love then, becomes the definition of sin and how we can determine what is pleasing or not pleasing to YHWH. Stated as a negative, it allow us to focus on the positive - Love. When we focus on becoming and behaving as Love in this world, we have less chance of being not-Love, and we can know in ourselves that what we are is either Love or not-Love.
Next: On The Gospel - Coming to God