Chastity is a virtue. That is, chastity is a good habit that human beings develop through practice over time. Chastity is also one of the fruits of the Holy Spirit. The virtue of chastity is frequently rather simplistically understood as 'not having sexual intercourse.' The association is often made to virginity and its preservation as was the case with the so-called 'chastity belt'. But this is not the essence of chastity., The very notion of a chastity belt is contrary to the idea of chastity as a virtue requiring the free choice of the person. Rather, chastity has to do with all experiencing. It is about the appropriateness of any experience. Ultimately, chastity is reverence: and sin, all sin, is irreverence. To be chaste is to experience people, things, places, entertainment, the phases of our lives, and sex in a way that not violate them or ourselves. To be chaste is to experience things reverently, in such a way that the experience leaves both them and ourselves more, not less, integrated (Rolheiser, 1999 pp. 201-202).

Sin, as action, means willingly and freely choosing to do something that we know is bad or wrong. Paradoxically, sin commonly involves choosing to do something that we somehow think is good. In his letter to the Romans, St Paul wrote, 'For I do not understand my own actions. For I do not do what I want, but I do the very thing I hate… . For I have the desire to do what is right, but not the ability to carry it out. For I do not do the good I want, but the evil I do not want is what I keep on doing' (Romans 7:15-19). Like St Paul, we too are basically good, created in the image of a loving God who wants us to live wholeheartedly and who invites us to freely return that love in the way we relate to God and others. With the capacities of reason, free choice and love, we are capable of freely returning God's love for us. Yet we are also flawed. We experience our own faults and weaknesses as well as the faults and weaknesses of others. We can find ourselves knowing what is good and right yet struggling to do what is good and right. When we know what is right and good and nonetheless choose to do something other than that, then we sin.

Another way to think about sin is to think about it in terms of our relationship with God. God wants us to flourish, to live whole-heartedly. God has created the world in a way that makes it possible for us to flourish provided we choose to do the morally right thing in line with the way God has intended. Consequently, when we choose to do the morally wrong thing, we are not simply choosing something which is less good for our own flourishing and the flourishing of others, but we are choosing something which is against the good that God wants for us and for everybody else. Consequently, we are choosing against God. As Ronald Rolheiser (1999, p. 202) notes, 'All sin is irreverence.'

With freedom comes responsibility. We are responsible for our moral behaviour because we are made in God's image as rational beings, capable of knowing what the morally right and good thing to do is and as free beings, capable of choosing to do the morally right and good thing. These two capacities, to know and to choose, together form what is called conscience. Loosely translated, conscience means 'with knowledge'. In other words, when we make moral choices, we make them based on what we know about the goals we want to achieve, the ways or means to achieve them, the circumstances in which we need to achieve them and the consequences of both the means we choose and the outcomes we achieve. When we have weighed all these things, we make a judgment based on our knowledge of what the morally right thing to do is. We are then obliged to follow our conscience and do the morally right thing, taking responsibility for our decision.

Sin is not simply about choosing to do something bad or evil. It is always about faulty judgments and subsequent flawed choices about what is good and right; sin is missing the mark. This can happen in two ways. Sometimes it is about choosing to achieve something what we think is good, though in reality when all is considered it is actually bad. Sometimes it is about choosing to achieve something that really is good, but doing so at the expense of things that are really greater goods and therefore should take precedence. For example, the murderer chooses to kill someone. But when he or she kills another person, that action is motivated by some mistaken understanding of a good thing that he or she hopes to achieve through the murder. Or maybe there is some really good thing that he or she hopes to achieve but at the expense of something that is a greater good in this case, the life of an innocent person. Consider the first case. A person might kill another human being in the belief that this achieves justice. But this is a mistaken understanding of justice. Or, as a second example of the first instance, perhaps the murderer is doing it because he or she actually desires to be 'evil', and believes it would be 'good' to be 'evil'. For the murderer, being 'evil' is a 'good' thing, though in reality this, of course, cannot be so. As an example of the second case, perhaps the murderer really does get some pleasure out of killing other people. Pleasure is really a good thing, but it is wrong to choose it over, in this case, the life of another person. Justice, pleasure, relief, and even 'evil' in this sense are all 'good' things in the mind of the murderer, because they are all things that are desired by the person acting, by the murderer in this case. But the murderer's actions remain objectively sinful, and remain morally wrong. They can never be morally right, regardless of the 'goods' that the murderer sees in them, be they real goods like pleasure, or imagined one's like 'being evil'. And this is so because the murderer cannot objectively defend the notion that any of those good or supposedly good things provide sufficient reason for wilfully killing another person. This is especially the case since the murderer's subjective perception of the good thing itself is mistaken or 'disordered' (such as wanting to be evil, or believing that killing someone achieves justice, or believing that one's own pleasure is a greater good than the life of another person). For more information on how the Catholic Church works out what is objectively morally good, see the section on Natural Law.

The severity of the sin, of the wrongdoing, is traditionally divided into two categories, venial sin and mortal sin. Mortal sin is the more serious of the two. Mortal sin is a conscious and freely chosen turning away from goodness, from the ultimate good and from God. It is a free rejection of our capacity to love and of our capacity to seek and find the truth. Mortal sin is a rejection of what we know to be the right thing to do in our conscience. In other words, it is a rejection of our very own dignity as beings created in the image of God. Such sins are called mortal because, in the language of the tradition, mortal sins lead to death and eternal damnation in Hell, unless the person sincerely seeks forgiveness. But one doesn't need to believe in Hell, or damnation, or eternal punishment to realise that the kinds of wrongdoings that are called mortal sin can have very serious and sometimes really deadly consequences for the flourishing of the whole community. For example, in the case of murder, in addition to the death of another person, there is significant trauma associated with suffering, anger, resentment, mistrust, fear, financial burdens and costs, disruption of work, destruction of families, and so on. There are specific conditions that must be met for a sin to be a mortal sin. First, it must be done with full knowledge; second, it must be freely chosen or willed, and third, it must concern grave or serious matter. Grave matter are those things that concern a fundamental good of the human person. Grave matter includes unjustifiably killing or physically harming a person, taking something that does not belong to you, having sexual relations with someone who is not your spouse, and withholding the truth from or deceiving people who have a right to certain information from you. In other words, a sin is only mortal in the strict sense when you freely choose to do it, knowing that it is the wrong thing to do. Of course, we are also very good at deceiving ourselves about what we really know, or finding ways to justify our behaviour to make it look like we didn't know or didn't choose. Being really honest with ourselves about these things is essential if we are going live whole-hearted, morally responsible lives. Whether a sin meets the strict definition of mortal sin or not intentions and actions must be wrong when they break down the kind of just and loving human community that God desires for us and that we really should desire for ourselves. Such actions break down the kind of community that we described in the previous section about Love, being free and being responsible means avoiding doing the wrong thing and trying sincerely to do the right thing for ourselves and for others.

There has been much theological debate about the nature and sources of what is referred to as 'original sin'. The ongoing discussion about original sin goes back to the time of St. Augustine though Augustine did not use that term. Original sin was understood in relationship to the universal saving work of Christ. The theological question was: If we are saved by Christ's death and resurrection for life with God, what are we saved from? Essentially, the answers to the 'from', prompted the theological construct of original sin. The idea is basically that the first human beings created by God, our original parents, were also the first sinners. Sin and death entered the world when they chose to eat the fruit of the tree of knowledge of good and evil, which they were told by God not to eat. As daughters and sons of the first human beings we are all inheritors of the capacity to do the wrong thing, even when we know it is wrong. We all experience life as struggle to survive against the odds (Genesis 3). However, this Biblical myth itself aims to explain something that we commonly experience. Something that, over the centuries, we have realized is far more complex than a simple choice to disobey God.

Fundamentally, the reality of sin's impact is very much part of the human condition. This is true of the individual, of society and of culture. This means that we can have distorted perceptions of what is true and misguided responses to what is good. In other words, when Paul, in Romans 7: 14-23, speaks of the 'inner struggle', he is speaking not just personally but about the condition of humankind as a whole. This struggle is between the spiritual self (pneuma) that seeks God, truth and goodness as opposed to the unspiritual self (sarkikos), which resists or opposes God, truth and goodness. Importantly, this conflict is not between spirit and body in the literal sense that we understand these terms today. Remember, we are a unity of mind, body and spirit. Rather, within the whole human person, there are tendencies or desires which sometimes feel like they have a power of their own. We experience such tendencies and desires as being at odds with other desires that we may have, desires about the kind of person we want to be, the kinds of things we want to do and the kinds of goals we want to strive for. In the context of relationships and sexuality education, such tendencies might include feelings of lust, a desire solely for sexual pleasure, the desire to possess or have control over other people, the desire to have other people desire you sexually in a way that gives you control over them, the desire to hurt those whom you think have done you an injustice, or just to hurt someone or yourself. Moreover, we often experience the world in such a way that our efforts to be and do good seem futile, as if we are left with no choice but to allow certain bad things to happen, or even to do bad things against our deepest intentions. Or, frequently, we find ourselves justifying the things we do, either by finding ways to say that actually they are okay (e.g., 'everyone's doing it', 'my friends will only respect me if I do it', 'they had it coming' or 'you have to live in the moment') or by making excuses for our inability to do otherwise (e.g., 'I was just following orders', 'I was drunk and didn't know what I was doing', or 'I am a very passionate person and so couldn't control myself in the heat of the moment'). From a Catholic perspective, the deep-seated nature of these experiences of ourselves and our society as sinful and the sense that we cannot overcome these bad things on our own, lie behind the belief that an intervention by God is ultimately necessary to save us from our own failings—from original sin and from our personal sinfulness. This intervention came in the form of the life, death, and resurrection of Jesus Christ. God helps those who turn to God for forgiveness, wisdom and strength. Through God's help, our weaknesses and failings can be brought to consciousness, healed and transformed.

We must be careful about balancing two things: first, the reality of the influence of evil and sin from sources beyond our control, and second, taking personal responsibility for what is within our control. Neil Ormerod (2007) offers a contemporary interpretation of original sin in terms of the experience of victimhood. In doing so, he highlights the question of responsibility and those factors that lessen or, even remove responsibility in certain human situations. The human reality is that we are influenced by genetic, social and cultural factors that are, to a lesser or greater extent beyond our control. In the light of such factors Ormerod makes the point, regarding original sin, that we are 'first and foremost sinned against'. From the time of our birth and into early childhood, this being 'first and foremost sinned against' entails a 'human brokenness, an interior shattering or distortion of consciousness that muddies our search for direction in the movement of life' that brings with it a 'weakened sense of our own worth which inclines us, with a statistical inevitability, to sin' (p. 79; citing Moore 1985, xiii).

However, does it end there? Are we caught in a deterministic-type cycle that offers no hope? We return to our Christian tradition. The saving and merciful action of Jesus is mediated through the Church. But it is also mediated, that is, it is present and active, in all those life-affirming, love-affirming, and justice-affirming aspects of human experience such as family, relationships and personal example. Our encounters with God, in the Church, in the depths of our being and in those positive human experiences, can heal moral blindness, prejudice, distorted desires, and self-centred passions while directing our longings for personal worth in ways that seek what is truly good and life-giving in God. Jesus, then, all things are made new, all things are restored and redeemed. Christians believe that baptism removes the stain of original sin, allowing us into the reign of God. In other words, we are no longer held responsible for things we did not choose to do. However, we are still held responsible for our sins, that is for those wrongs which we freely choose. The good news is that here too, forgiveness, healing, and reconciliation with God and others is possible.