Moral Theology is described by Gregory C. Higgins in Christianity 101 as ‘the branch of theology concerned with the proper conduct for Christians; this is known as moral theology, or Christian ethics.’  Morality can be described as right conduct or virtuous behaviour. Ethics has been depicted as the science of morals and also as a branch of philosophy which determines right from wrong behaviours. The Catechism of the Catholic Church teaches us about free will and how that freedom ‘makes man (and of course woman), a moral subject. When he acts deliberately, man is, so to speak, the father of his acts. Human acts, that is, acts that are freely chosen in consequence of a judgment of conscience, can be morally evaluated. They are either good or evil.’ 
Gregory C. Higgins believes that Jews and Christians adhere to as he describes it a ‘divinely willed moral code’  so the foundations of Moral Theology are built on the Ten Commandments which God gave Moses on Mount Sinai and are continued by the Torah. (‘Torah’ refers to the Five Books of Moses: Genesis, Exodus, Leviticus, Numbers and Deuteronomy. The word Torah means teaching. The Torah is the principle teaching instrument that God uses to communicate revealed truths to the Jewish people, who are our forefathers and consequently these truths are also revealed to us as Christians as we study the history of our faith.) Moral theology is also revealed through studying the Prophets and the Books of Wisdom.
As Christians we look to Jesus as our Teacher and Leader in all things to do with Christian Ethics and Moral Theology. Jesus’ life was the gold standard for all of us. According to Higgins the Synoptic Gospels, (those written by Matthew, Mark and Luke referred to as synoptic as they share a common or similar viewpoint), reveal many of the moral and ethical concerns of the early church. Much of Paul’s correspondence reflects and also attempts to address these concerns. We will also find Moral Theology in the Catholic, or General Epistles these are the letters written by James, Peter, John, and Jude. These epistles are addressed to all Christians for the edification of the faith.
When St. Paul speaks about moral virtues that Christians need to develop to advance in their spiritual lives he specifically mentions faith, hope, and love (1 Corinthians:13), these are known as the ‘three theological virtues’  In Galatians 5:22 Paul expands on some other virtues by mentioning, joy, peace, patience, kindness, generousity, faithfulness, gentleness, and self-control.
In describing the Catholic or General Epistles Higgins touches on the ‘faith and works’ dynamic that has been so divisive between different sects of Christianity over the years and sadly continues through present times.
Clement of Alexandria one of the Early Church Fathers believed that humans were made in the divine image and as God is rational and as humans we are also capable of rational thinking, plus we have and enjoy the freedom of our wills. So Clement stated that man ‘would be subject neither to praise nor blame were he not free and were his beliefs and conduct not always completely within his power.’ Therefore following Clements reasoning human beings are capable of choosing right over wrong, good over evil, resistance over temptation and triumph over failure. When they don’t they are responsible for their actions.
Plato named the Four Cardinal Virtues as, Prudence, Justice, Temperance and Fortitude, these Virtues were adapted by the Early Church Fathers, St. Ambrose, St. Thomas Aquinas and also St. Augustine of Hippo who in explaining them wrote ‘As to virtue leading us to a happy life, I hold virtue to be nothing else than perfect love of God. For the fourfold division of virtue I regard as taken from four forms of love. The object of this love is not anything, but God, the chief good, the highest wisdom, the perfect harmony. So we may express the definition; thus temperance is love keeping itself entire arid incorrupt for God; fortitude is love bearing everything readily for the sake of God; justice is love serving God only, and therefore ruling well all else, as subject to man; prudence is love making a right distinction between what helps it towards God and what might hinder it.’ 
Thomas Aquinas writings were heavily influenced by Aristotle who taught of our ‘human nature’ which he believed was comprised of the basic needs all humans have plus individual character traits including inclinations and desires that are uniquely human. Aquinas’ teachings built on Aristotle’s philosophies; Aquinas himself also believed in human nature and stated that the qualities or gifts humans possessed were given by God. Aquinas also believed that mankind has a fallen nature and to become reconciled to God we have to cultivate the four cardinal virtues.
Immanuel Kant appeared during the Enlightenment, an optimistically named period where human beings attempted to answer all of the difficult outstanding questions of Moral Theology. Kant’s moral theory stemmed from his belief that as rational human beings we all have a moral obligation to do the right thing for the right reasons.
Enlightenment scholars made some progress in their day but moral theology is an evolving theology since we still struggle today with questions such as ‘When does life truly begin?” and “Would God approve of artificial insemination?” and “Is it right or wrong to artificially inseminate a 70 year old woman who wants to be a mother?” “Where does God stand on stem cell research?”
Every age has it own questions to answer as human progress and technology bring advances not even dreamed of by our ancestors who probably studied by candlelight, while translating scriptures from the original Greek language, and who also lacked the plethora of Theological works that are available for us to study today. Yet these prominent early Theologians have winnowed and harvested much fruit from their studies that have benefited many subsequent generations of students. (Including several popes)
‘Until modern times the relationship between religion and morality was generally taken for granted, and writers as far different in philosophy as Plato and Avicenna, or in theology as Aquinas and Luther, never questioned the basic truth expressed on Mount Sinai, when Yahweh gave the Jews a Decalogue whose first precepts were to honor God as a foundation for the secondary precepts of the moral law. But something new has entered the stream of human thought, a concept of man’s autonomy that wishes to dispense with religion in its bearing on morals, on the grounds that the very notion of religious values is only a mental construct’. 
The paragraph above succinctly explains why we need Moral Theology and why it is so necessary in our modern world that often declares it has no need of God. Much Moral Theology is based on the Four Cardinal Virtues, prudence, justice, temperance and fortitude. Paul tells us of moral virtues naming faith hope and love and states clearly that the greatest of these is love. Many unbelievers, some former believers, and some, who call themselves believers while espousing behaviours contrary to Gospel values, state that ‘to each his own’ is the way to live your life. We talk glibly of people ‘living their truth’ while engaged in living lives that are clearly and unequivocally contrary to Bible teachings.
Many people call practicing Christians ‘judgmental’ because we speak out for Gospel values, the values that Jesus died proclaiming. Moral Theology is a necessary cornerstone of faith today. I believe that it will contradict moral relativism at every turn. Jesus called Himself, the Way the Truth and the Life. There is only truth in Him, His life, His teachings and His Gospel. But the message has to be always proclaimed in love. John 3:17-18 ‘For God sent the Son into the world, not to condemn the world, but that the world might be saved through Him.’ Christianity is a very necessary moral compass needed in this sad and sorry world seeking for love through all the wrong places, people, institutions and unfulfilled and empty promises. Love can only be found in love, by love and true love is Jesus Christ, love personified.
Jesus showed us truth by His life, death and resurrection from death. Yet the greatest lessons Jesus gave were through His Words and His Teachings. Each word, each syllable has much to teach us today in how we are to live in right relationship with God and our fellow human beings. We can study the words to death but at some point we have to put into practice the teachings or we are just chaff in the wind. I don’t want to involve myself in the old faith versus works debate, but simply put if I have the most amazing gift in the world and I keep it all to myself, I am selfish. If I have the most amazing gift in the world and I want to share it and take action to share it with as many others as I possibly can, I am obeying the call of love in my heart.
Matthew 25:35-40 “For I was hungry and you gave me something to eat, I was thirsty and you gave me something to drink, I was a stranger and you invited me in. Then the righteous will answer him, ‘Lord, when did we see you hungry and feed you, or thirsty and give you something to drink? “The King will reply, ‘I tell you the truth, whatever you did for one of the least of these brothers of mine, you did for me.”’
We know by these words of Jesus that loving Him and His Gospel entails loving all of our fellow human beings. Sharing what we have in practical terms with those who have not is a requirement of a baptized Christian Catholic.
Studying Moral Theology will only bring into contrast more starkly the ways of the Gospel and the ways of our fallen world. We are all called to be lights in the darkness. Learning about Moral Theology is another lit candle that challenges the darkness.
Gregory C. Higgins, Christianity 101, p369
 Catechism of the Catholic Church, Article Four, 1749
 Higgins, p369
 Ibid, p370
 Gregory C. Higgins, Christianity 101, p374
 St. Augustine, The City of God, p235
 Hardon S.J., Fr. John A. “Father John A. Hardon, Archives.” The Real Presence Association. Available from http://www.therealpresence.org/archives/Moral_Theology.htm. Internet; accessed11 December 2008.