Ethics is the art and science of the human condition. Some philosophers, and some scientists, maintain that ethics is about 'value judgments' that are completely separate from scientific knoweldge. This can no longer be maintained. Ethics is concerned with how we can rationally decide the question of 'What to do for the Best?' in any specific situation involving human behaviour.
In everyday words, ethics is about what we ought to do, what decisions are right or wrong and what behaviour is good or bad. There are often situations where we cannot work out what is for the best. Then we can only make a rough judgement based on inadequate evidence.
Ethics can only become a rational subject if we can identify some general principles to guide us. The principles sketched here are based on the scientific world-view. Humans are social animals and have to learn to live together. It is of great importance to have as full information as we can obtain about any situation in order to make informed choices on the evidence available. The way we decide what is right in particular circumstances is to apply reason to the facts of each case.
Individuality. Our first duty is to survive and prosper for ourselves. This will mean to seek pleasant experiences and to avoid pain, though deferment of pleasure now may mean greater pleasure or less pain in the near future. This will mean developing what talents we find we have and making good use of them. This will also involve making friends and not enemies, so really it has wider implications and is not mere selfishness which takes no account of other people, but self-interest which recognises that we exist in a social context.
Sociality. Our second duty is to those nearest to us. This will usually mean our immediate family, friends and local society. But it also applies more generally to those we are able to influence, which in the age of the internet may be much further afield. The criterion of what is good is the evolutionary one of that which leads to survival and flourishment of the society. This is a form of utilitarianism.
Universality. Our third duty is to the wider world. Having taken account of our own interests and those of our society, we are able to look ever wider and exercise idealism. Ultimately this could take in the whole universe and future time, but our knowledge will seldom, if ever, enable us to make decisions on such a cosmic scale.
Religious codes of behaviour usually take the form of a series of commandments, which are absolute moral rules intended to apply in all circumstances without exception, but they are only interpreted in this way by extremists. In practice it is necessary to make all sorts of exceptions.
For example: 'Thou shalt not kill', is a useful general rule, but if we are attacked should we not defend ourselves? Should we not have armed forces to defend our society, and authorise members of those forces to kill, when necessary, to defend our interests? Does the rule imply that birth control and abortion are immoral? Does the rule also extend to killing animals for food, or for obtaining medical knowledge? Does it apply to insects that spread disease, or to the harvesting of plants for our nourishment? Evidently there are many cases where the general rule is unethical.
Secular ethics recognises that such general rules need detailed interpretation according to circumstances. There are no simplistic rules that can be applied to solve every ethical problem. It is however perfectly possible to take ethical questions seriously without referring to religion. 'What to do for the best?' can require a lot of hard thinking, gathering of evidence, and trial and error. Even then we may get it wrong, as subsequent history may prove.
I hope to follow up the above account with some detailed consideration of specific ethical problems. Meanwhile here are some links to help you think.
Philip Pullman University of East Anglia Lecture
Thomas Ash Are Morals Objective?
Alec Rawls Christian and Secular Natural Law.
Paul Kurtz Can sciences help us with ethical judgments?
Brian E. Hodges Health Career Model.
Moral Objectivism
Edward L. Ericson Ethical Humanist Religion.
R. B. Meyer "... by 3000 BCE the Egyptians possessed a moral code far superior to the Ten Commandments and the raving Hebrew prophets."
The Instructions of Ptah Hotep The oldest book of ethics.
J. Michael Sproule Ptah Hotep as classic rhetoric.
Guardian Letters "... the humanist agenda is ... parasitic upon religious belief ..." Giles Fraser.
Guardian Letters "Good and kind people outnumber all others by thousands to one ... Every spectacular act of evil will be balanced by 10,000 acts of kindness, too often unnoted and invisible as the 'ordinary' efforts of a vast majority." S. J. Gould.
Relativism;
Steven D. Schafersman Critical Thinking.