This is the first post on Christian ethics in my ongoing series, theology in bullet points. The first unit in this series had to do with God and Creation (book here), and the second unit was on Christology and Atonement.
We are now in the third and final unit: The Holy Spirit and the Church. The first set of posts in this final unit was on the Holy Spirit. The second set was on the Church. The third set was on sacraments.
Christian ethics is, at its base, a virtue-based ethic.
1. There are two broad approaches to ethics. The one focuses primarily on how we are to behave (act based ethics). The other focuses more on our motives and character (virtue based ethics). The most mature Christian ethic, at its root, takes a virtue based approach for its foundations.
It is not, of course, that actions are insignificant from a Christian point of view. It is only that Christianity is more interested in the motivations and character from which actions flow than with the actions themselves. The same act can be either wrongdoing or virtuous, depending on the motivation for doing it.
2. Approaches to ethics that focus on our actions tend to be of two sorts. One asks what our duty is in relation to each action we take. The other asks about the consequences of our acts when we are considering what to do. Both of course play a role in Christian ethics, even though these questions do not stand at the heart of the most mature Christian ethic.
The first approach is the duty-based approach, a "deontological" approach. What is the right or wrong thing to do?  This approach, in its simplest form, can think in black and white terms and sometimes speaks of moral "absolutes," which are considered to be acts that are always in every case right or wrong actions.
There are certainly some moral absolutes in Scripture. Jesus summarizes the entire Law in the twin commands to love God and love neighbor (e.g., Matt. 22:34-40). These are the most fundamental Christian moral absolutes.
However, even in this case, Jesus pushes the absolutes to the level of principle, not of individual acts. There are some individual acts that are always wrong. It is hard to imagine a situation where adultery or the murder of the innocent would be justifiable. Because these acts would be wrong in every context, we can consider them moral absolutes.
But even in these situations, the act of sex itself is not sinful, but the context in which one is having it. The sex act is good within marriage. Similarly, there are places where the Bible assumes that killing is not sinful, even if it is not ideal. The Bible assumes that death will occur in war and capital punishment. 
It is thus the context of an act, and especially the intention of the person doing the act in that context, that speaks most to the moral character of the act.
3. More often, the Bible assumes that there will be exceptional circumstances to Christian "duties." So we are generally to obey those in authority over us (e.g., 1 Pet. 2:13-17), but there will be exceptions (e.g., Act 4:19-20). We are to be people who tell the truth (Eph. 4:25; Matt. 5:33-37), but there may be exceptions (e.g., Josh. 2:2-6). One might construct, as it were, a hierarchy of values to decide when I higher value takes precedence over a lesser on.
However, a more mature approach to ethics does not take on this Pharisaic character. In the Bible, it was the Pharisees in the Gospels who had a legal approach to ethics, and it was the Judaizers with whom Paul sparred who viewed ethics as a matter of dos and don'ts. When Paul argued that believers are not under Law but under grace, he was in effect indicating that a Christian ethic is a virtue ethic, not an act based one.
A more mature Christian ethic asks what course of action fits best with the love of God and the love of neighbor. The more mature Christian ethic does not ask, "What is my duty?" or "What is right and wrong?" but "What would be most pleasing to God in this case?" and "How can I most show God that I love him in this instance?"
4. A second act based approach looks to the consequences of an act to determine what choice to make, a "consequentialist" or "teleological" approach to ethics. It is not that such questions are irrelevant. Indeed, if the love of our neighbor is our guiding principle, then we will strongly consider what the effect of our actions is on others.
As we saw in previous articles on sin, one can sin unintentionally by wronging another person without intending to do so. Christ died for these sins as well as for the much more important intentional ones. But it is the wrongdoing that is a matter of our conscious choice that is of most concern to God.
When it comes to structuring a society, the consequences of actions become a matter of great concern. What is the way of structuring a society that 1) brings about the greatest good to the greatest number of people 2) without harming or wronging individuals within that society? The notion that "the end justifies the means" is generally rejected by Christians, which suggests that any path to a goal is legitimate if the goal itself is good. There are good paths to good goals, and there are bad ones.
But the consequences of an action are not the starting point for a mature Christian ethic.
5. The starting point for a mature Christian ethic focuses on the fact that we are in Christ and that Christ lives within us. It focuses on who we are, which demonstrates itself in our motivations and intentions, which then demonstrates itself in our actions. "I have been crucified with Christ and I no longer live, but Christ lives in me. And the life that I now live in my body, I live by faith, indeed, by the faithfulness of God’s Son, who loved me and gave himself for me" (Gal. 2:20, CEB).
The Holy Spirit within us leads to a certain fruit in our lives. "The fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control. There is no law against things like this" (Gal. 5:22-23). By contrast, "Those who belong to Christ Jesus have crucified the self with its passions and its desires" (5:24).
This is a virtue-based ethic. It is one that focuses on our relationship with Christ and on the kinds of motivations and intentions that naturally result, more than on the acts themselves.
6. These are the priorities of a mature Christian ethic. It begins and ends with God. It begins with God for we are not able to be or do good apart from the power of God. It is the power of the Holy Spirit that enables us to love God and our neighbor in the first place.
Empowered by the Spirit, it is a relational ethic. We love God, which informs our motivations and choices. God changes our hearts, which in turn changes our actions. When Paul speaks of the transformation of our minds in Romans 12:2, he did not mean our pure intellects or some purely cognitive dimension of our minds but our attitudinal dispositions as they lead to life. The rest of Romans 12-15 plays out this transformed mind, the key to which is love (Rom. 13:8-10).
In this Christian ethic, acts play a more central role in our past need for forgiveness, for all have sinned (Rom. 3:23). In Paul's system, acts are the focus of the old covenant, for "all who rely on the works of the law are under a curse; for it is written, 'Cursed is everyone who does not observe and obey all the things written in the book of the law'" (Gal. 3:10).
However, under the new covenant, under the power of the Holy Spirit, our virtues become the focus of living--faith, hope, and love. It is not that how we act is insignificant. It is just not the focal perspective through which ethics is viewed. Therefore, Christian ethics that focus on actions, on rights and wrongs, or on absolutes are less mature than those that focus on our relationship with Christ and Christian dispositions toward God and others.
The Christian ethic, at its base, is a virtue based ethic.
ET2. The foundational value of a Christian ethic is love.
 In every version of the stages of moral development, the "law and order," rule-oriented approach to ethics is a lower pattern of moral thinking than those that focus more on moral principles or moral character.
 In a later article, we will consider under what circumstances killing might not be a sin. It is doubtful, however, that God ever considers the human killing of another as "good," even if in some circumstances it may not be sinful.