If I could add to what Jonathon and Grahame have already posted. This teaching is one that was taken up by Christ in the Parable of the Good Samaritan. In short the basic answer Christ is giving is that yes, we are our brother's keeper. And it is an onerous responsibility. The end point lesson of the Parable of the Good Samaritan is that we stay with our brother (and brother here I don't think is to be taken in the context alone of "blood brother" but more in the general biblical sense of "neighbour" or any person in distress) until the distress has been adequately addressed and the person is, in colloquial language, "put back on the their horse and able to continue their journey". In ordinary civil law in our country we see this principle enshrined in the law of the road that following an accident, in law we are obliged to stop and render assistance to any person who might be injured. People who engage in "hit and run" accidents are usually prosecuted under this section of the Traffic Act. In a sense they are being prosecuted under a section of the Law that has been passed down to us from the teaching in the Parable of the Good Samaritan. In our work-a-day lives we all go through experiences, sometimes big, sometimes small, where we are playing the part of the Samaritan or we are playing the part of person in need of the assistance of a Samaritan. My own long reflections on this matter at the practical level have led me to the conclusion that often the difficulty in living out this teaching is at the practical level. Obviously there is a practical limit either to the amount of assistance we can render -- this might be caused by the limits of our own skills, limits of time, limits of resources -- and assessments might have to be made as to what is a fair assessment of when the person in need of assistance has received sufficient assistance that they are capable of continuing their journey without further assistance. This is one of the places where I think the ordinary application of moral theology is advancing in leaps and bounds. Younger people today seem to me to have a much better understanding of this sort of territory than older people even if they might not necessarily be accepting of a lot of other aspects of moral theology or Church teaching. The correct interpretation of these matters is that the Parable of the Good Samaritan, and the places where that is interpreted -- for example the Catechism of the Catholic Church -- gives us a broad overview of the moral principles that are involved. The practical application of those general principles is another matter and can lead to many anomalies where something can appear to be morally wrong in one context but in one almost exactly similar where just a few of the descriptive parameters are changed the exact same action can be classified as morally correct or morally neutral. Let me try and provide an illustration of this using a deliberately stretched illustration of two extreme scenarios. Say two traffic accidents occurred and in both cases they occurred on a country road with not that much traffic. The first accident involved one car hitting a tree. There was only one person in the car, the driver. She was critically injured in the accident. There was not much traffic on this road. However, quite coincidentally, 10kms further up the road a short time earlier a far more horrific accident had also occurred. This accident though involved a freight train that had crashed into a tourist coach and forty passengers had been killed or were critically injured. The moral scenario I am about to play out is focussed on the scene at the first accident involving the woman who was critically injured when her car hit a tree. It also focuses on the different responses of two different people who might have been the first person on the scene of that accident. In the first scenario, the first person to arrive on the scene happened to be a doctor who was actually on his way to the second accident. Does he have a moral obligation to stop at the first accident he comes across? The answer is "yes". The obligation is both moral and it is legal (under the Traffic Act). We assume here that he already knows that the carnage at the second accident is horrific even if he does not know the exact level of the carnage. He certainly knows that more than one person has been critically injured. What should his moral response be? I should imagine his response is to stop, to make a quick assessment of the extent of the injury, to make the patient as comfortable as he can in as quick a time as he can and to use his mobile phone to alert the police or some other suitable authority to the existence of this accident and to as quickly as possible proceed on to the second accident even if it were to mean that this accident victim was to be left unattended for a short period of time. We'll assume his phone call is to the police. The matter might possibly proceed to a court for him failing to remain at the scene of an accident but I am pretty sure that in the eyes of the Law, and in moral law, he would not be guilty of failing to be his brother's (or in this case "sister's") keeper for failing to stay at the scene of the accident. There was a limit on his time and his expertise was required elsewhere at a far more serious accident that had occurred at the same time but a little further down the road. In the second scenario we can assume that the doctor has now departed the scene and a second driver arrives on the scene of the first accident. He probably does not even know that a doctor has already examined the injured driver and made her as comfortable as he could. This second driver stops and examines the scene but decides that he gets squeamish at the sight of a bit of blood and although he does try to comfort the woman for a few minutes he also has in the back of his mind that he is late for an appointment with the bank manager at the next town. He uses his phone to telephone an authority (which happens to be the ambulance rather than the police and no knowledge has yet been passed to the ambulance people about this one car accident so they are not able to tell him that a doctor has already been on the scene). So far his actions have been morally and legally correct. He has stopped, although squeamish about the blood, he has rendered what assistance he could by telephoning the authorities and endeavouring to comfort the woman. However, after a few moments he becomes impatient and decides that his appointment with the bank manager is more important than waiting around with this injured woman until the ambulance arrives and professional care is available to the woman. He hops in his car and continues his journey. Is this man now guilty of a moral failing? Is he guilty of a legal failing? I would be pretty confident that in both cases the answer would be yes. The excuse of the appointment with the bank manager would not be considered sufficient reason for him to leave the scene of the accident. The doctor though did leave the scene of the accident in almost identical circumstances and yet there is no moral wrong in his action. He had an over-riding responsibility that made his action in breaking the law (moral and legal) acceptable and, in fact, the morally correct action to take. Every day of our lives we face moral dilemmas similar to this one. Church teaching cannot spell out what is the correct moral response down to the precisely dotted "i" and crossed "t" in each situation. Using the general principles though the mature, reasonably educated person should be able to reason through what the correct moral response should be.