The very word morality comes from the Latin mores , which among other things means 'character'. Your character is your moral identity; the kind of person that you have made and are making yourself to be by the moral choices that you make. We are like sculptors, both the agent and the clay that is being molded. We make ourselves; we sculpt our character. There is nothing more intimately ours than the character we have shaped. Of course, character is not the same as 'personality'. You and I have inherited many personality traits through DNA, and other traits have been determined through an environment we had little control over. But character is entirely yours, more intimately yours than anything you possess.
Morality has to do with human action; specifically, it has to do with good and evil in human action. An individual human person is like a blank cheque: there's a pre-existing structure to the cheque, i.e., your name and address at the top left; the name, branch and address of the bank; a line for the amount to be written, and a small line for numbers, a line for the signature, background colors, a number at the top right, a design, etc. But there are also blank spaces for us to fill out. Similarly, human persons have a determinate and structured nature, a rational nature with a host of powers and sense appetites some of which can be governed by reason (i.e., the will and the sense appetites) and some of which cannot (the power of growth, eyesight, sense memory, etc.). But there are spaces for us to fill in and determine as we choose, and we can fill those spaces with a determinate identity that is good (complete, ordered, harmonious), or one that is morally deficient (bad, much to be desired, dilapidated).
The moral law is the law that governs human choices and, if followed, leads a person on a course towards moral integrity, that is, moral goodness. Evil is a deficiency, a lack of fullness that ought to be there. The moral law (the natural moral law) consists of natural precepts (often naturally known) rooted in natural tendencies (called basic intelligible human goods). It is like a road map indicating where we ought to turn and what direction to take, and what turns to avoid. Of course, what makes these directions the right ones is the destination. If we are heading to Florida, we'd best not go East on the 401, but West, and then south on 75, etc.
Our destination, of course, is eternal life or union with God in the Beatific Vision. God is Goodness Itself; for God is Love, according to the First Letter of John (1 Jn 4, 8). Why does God create anything at all? Because God is Love, and love is effusive. What is effusive pours itself out, and so genuine love seeks to communicate itself beyond itself, to spread out, to give of itself. Love is self-expansive. Hence, God is self-diffusive. He created us in order for us to share in His goodness. God is Being Itself; for He revealed His name to Moses: I Am Who I Am. And so, the first thing God communicates or imparts to creatures is being (existence). It is good to be; it is good to exist. Creation is good; we read that in the first chapter of Genesis. To exist within this highly diversified universe is good; for it is a sharing in the goodness of God.
But God does not want to stop there. He reveals Himself in history, first to Israel, by entering into a covenant with Abraham and revealing Himself through his relationship to Israel (salvation history), and finally he reveals Himself in the Person of Christ, the Word made flesh. He came to save, to redeem (to buy back), but deliver us from death, which entered the world through sin. He reveals himself for the same reason that anyone of us would reveal ourselves to another: as an invitation to a deeper relationship. In other words, the goodness of creation is not enough for God's love of us. He invites us to Himself, to an eternal union with Himself. He came to reveal His love, a love that is visible from the cross. He rose from the dead, which reveals that He has conquered death, the death brought on by the sin of Adam. He has restored us to life. We too will rise to eternal life, with a glorified body, if we live in him and die in him. That is the good news of the gospel.
God invites us into Himself. He does not merely grant us a share in the riches of creation, but he invites us to the perfection of goodness, to possess Goodness Itself, Beauty Itself, Truth itself. To possess Himself in other words. And because of the death and resurrection of Christ, the grace of God once again flows through the veins of humanity. Divine grace, a sharing in the divine life, is available to everyone, to a sufficient level. This is what is referred to as sufficient grace. It is up to us to cooperate with that grace in order to merit an increase in grace (sanctifying grace).
The moral life is a movement towards the fullness of eternal life. In other words, the moral life is about becoming good - which is the condition for even wanting to possess God himself; for not everyone is loyal to the good and developing towards that end; some in fact love evil. Christian morality is about becoming conformed to the image of Christ; it is about decreasing so that Christ may increase in us, as John the Baptist once said (he must increase, I must decrease). It is about dying to self so that Christ may live fully in us and so that through us, Christ can invite others to himself. In other words, we are to become his hands, feet, eyes and ears, etc.
Most people see morality is restrictive: can't do this, can't do that, etc. But it is really about becoming more fully the person God intends for us to become. When God sees us, he looks at us through rose colored glasses. Yes, he sees us in all our warts and defects, but He sees us as He intends us to be; He sees us in all the perfection and splendor that is ours as He intends us to be in the Person of Christ. The moral life is about achieving that image, becoming a unique Christ, that Christ which He can be only in you individually. When you are the person Christ intends you to be, when it is no longer you who live, but Christ who lives in you, then Christ appears on the stage of this world uniquely - because you are unique. Christ has a new face, a slightly different face. It is your face, but your face has really become His face. No one can be that unique face of Christ except you. And when He is you and you are Him, you have a beauty that no one else can possess.
There is a secret to looking beautiful, and that secret is virtue. Aristotle understood this in the 4th century BC. A Greek word Aristotle used was kalon , best translated as moral nobility or the morally beautiful. It is a word derived from kaleo , the Greek word that means attractive, which is a property of a beautiful work of art. It is the cultivation of the virtues that brings harmony to the various faculties and emotions of the human person, and harmony is a property of beauty. And since the human person is a unity of spirit and matter, what takes place on the level of spirit is manifest in matter, especially the countenance. A person of moral beauty will have a face that radiates it, but a person who lacks that moral nobility will, despite being handsome or pretty, will lack a certain moral attractiveness. There is a unique beauty that is yours to grow into, or yours to become.
The first appearance of the moral law which directs us toward that initial stage of moral beauty comes in the book of Exodus: The Ten Commandments. These Commandments are the basic precepts of the moral law (love God above all things, reverence the name of God, keep holy the Sabbath, honor your father and mother, do not kill, do not commit adultery, do not steal and bear false witness, and do not envy others). These principles are very general, but the application of those principles within the contingencies of everyday life render the science of ethics much more complex.
In the New Testament with the coming of Christ, a higher moral law is introduced, one that exceeds the grasp of reason. We need a higher moral law precisely because we are called to a higher end, a supernatural end, namely eternal life, which is achieved as a result of living and dying in the Person of Christ. A supernatural end requires a supernatural morality. The basic contours of this morality are found in the Sermon on the Mount, beginning with the Beatitudes: Blessed are those who know their radical need for God, those who mourn the sinfulness of human beings, who are meek, who hunger and thirst for what is right, who are merciful, who are pure in heart and are peacemakers, and finally blessed are those who are persecuted on account of Christ. Moreover, if someone sues you for your tunic, give him your cloak as well, in other words, do not always stand on your rights. In the Old Testament, we were told: 'You shall love your neighbor and hate your enemy', but Christ commands us to love your enemies and pray for those who persecute you. Etc.
Christian morality is not so much following an external set of precepts. This new law is written on the heart, a new heart. The new law is actually about living in the Person of Christ, living each day with the strength that he provides for us to be able to follow him to Calvary. We have this ability because we participate in his life, we take on his heart and love with it, not with our own. We begin to see the world and others through his eyes. Our life becomes a sacrifice in his sacrifice. In other words, we begin to live out what we became in baptism, namely, priest, prophet and king. A priest is one who offers sacrifice. Our life becomes a life of sacrifice in him, that is, a life given over to him, that he may be himself in us. This is the Royal Priesthood of the Faithful. And we were anointed prophet as well. A prophet is a mouthpiece of God. one who proclaims the truth revealed by God. God is Light from Light, and so in him we become light. Our life is to be, on the whole, a proclamation of him, of his risen life, of the new life that he brings. And we were anointed king. A king governs a kingdom. He goes to battle, to war, to conquer and expand his kingdom. We share in his kingship, and so our life is a battle to expand the kingdom of God that he established over and against the kingdom of darkness. Although Christ defeated the kingdom of darkness, there are still battles to be fought, as Douglas MacArthur said at the end of the war: "the campaign can now be regarded as closed except for minor mopping up." These battles are fought not with conventional weapons, but with the armor of God (i.e., prayer, the word of God, Eucharist, and supernatural prudence). As Bolt has Thomas More saying in a Man for All Seasons: "God made the angels to show Him splendor, as He made animals for innocence and plants for their simplicity. But man He made to serve Him wittily, in the tangle of his mind".