The first possible theory is that God (or Gods) decides morality out of nothing (ex nihlo). If this is the case however then morality is purely arbitrary and based upon chance; what we perceive to be moral had an equal chance in another time of being immoral. For example, rape being seen as a pious and moral whilst charity and selflessness being seen as immoral and evil. In this sense, any deity could not be good as deities are simply good by their own definition. An argument against this view however, is that if morality were reversed we would have no concept of it ever being any other way.
The second of the possible theories is that morality is an independent standard by which God and humanity abides. However, there has to have been a creative mind behind this standard, something that can set rules that even God has to follow. If this theory is to be the case however then God is no longer the most powerful entity in existence, which would mean that he is not God.
St Thomas Aquinas is possibly the most influential ethical philosopher of all time, his text “Summa Theologioe” sets forward moral codes and theories that are still in use today. His text is based around the second of the two Euthyphro theories (that morality was an independent standard) and put forward three starting blocks for the basis of morality. The first of these is that God instills in people a set of moral rights and wrongs – we all know exactly what is right and what is wrong from birth and that without them we would have no basis for morality. Secondly, Aquinas believed that there is a singular ultimate rule of natural law of which god is the basis; it is possible for humans through reasoning and deduction to discover what this ultimate rule is. Finally, he believed that successive extra moral rules could be conceived from this one ultimate moral rule; any of these moral rules are therefore in accordance of natural law.
Hugo Grotius (1583-1645) later expanded upon Aquinas’ natural law theory. to produce the divine command theory. This is the view that an act is moral only as long as it conforms to God’s will. Emil Brunner summarizes this in 1947 as “The good consists in always doing what God wills at any particular moment.” According to this theory therefore it is because of God’s will that people are charitable and moral, any immorality stems from the person either not believing in god or deliberately going against god’s wishes. However this theory relies on the fact that morality itself is arbitrary. A.J. Ayer argues against this by saying ‘No morality can be founded on authority, even if the authority were divine’ However Leibniz argues against this by stating that god could be so unlike humans that he is beyond our comprehension.
The theories expressed above all rely on the premise that there is an all-powerful God with infinite power. Although god is the basis for a majority of world religions there are a few such as humanism that, although they have a moral code, they do not believe in a deity. This could equally be true for all religions, for example the British legal system is roughly based around the 10 commandments which also form the basis for Christianity. In this sense then morality of society is based upon religion, albeit one that has a possibility of being separate from god.