Here's the scoop: my school hosted a debate between philosophy professors last week trying to answer the question "Is God necessary for morality?", which was a nice two and half hour performance that I wanted to go see. Unfortunately, my grandfather swung by unexpectedly, and I spent time with him, only returning to campus when the debate was already mostly over. At first, I didn't care. Until I read the summary in the newspaper about it today. Apparently it was a rather heated debate. But, the core issue, the question at the heart of the discussion, is one that is patently simplistic to resolve, that I was not inclined to mourn the exercise in inanity that was most likely to have occurred when two people argue about theology with their agendas on their sleeves. Especially since I was able to read the summary of their arguments. So, I'll give my take on this little issue.
The reason why God could be seen as necessary for morality is if 1. God sets absolute, objective moral standards that humans must live by and 2. it is not possible to have objective moral standards without such divine commands.
Though number one may be true if you are willing to presume that a God exists, it really is not incredibly relevant to say that God sets moral standards, because if you suppose God to exist, then he supposedly standards and laws governing all aspects of existence, with morality being no exception. As such, it is akin to saying that "Since God exists, God exists". The creation of morality is all tacked on with the idea of God along with the laws of nature and existence itself, so if you accept the idea of the Biblical God, there is no use arguing over the rest of these points. Of course, in fairness, one could argue about how relevant the objective moral standards given to us by God are if many of his commands are outright ignored as illogical and irrelevant, or even deemed to be patently immoral in some instances. If morality comes from God, then what tells us which among God's law to follow, and which to deem as superfluous? (For instance, look at the Ten Commandments. How is that we feel that not killing and not stealing are more important than lying and not committing adultery, which are themselves more important than not working on the Sabbath and not respecting our parents? How is it that we know which is more horrible among the forbidden activities if they are all objectively wrong by God's law?)
The second point is a thought experiment in which one must disregard the idea of God deliberately overseeing our actions and commmanding certain behavior for a moment. Imagine a purely materialistic world, which is not overseen by any entities beyond our comprehension, and whose creation is a mystery of utmost irrelevance. Now, we have groups of people dotting this unwatched existence, and, supposedly, they should be able do whatever they damn well please. Of course, if that happens, if the people within each distinct group do not act within the confines of certain acceptable behavior, the group will not function as effectively, and will either be internally or externally destroyed due to this. In this sense, we give birth to morality as a social contract: commonly agreed upon behavior that will allow for social groups to function optimally, promoting fairness and cooperation in order to sure collective success and prosperity.
It only requires minimal thought to determine the consequences on a group of each within the limited society adopted a certain pattern of "immoral" behavior. If a group consisted entirely of rampant murderers, the society would be stripped down to nothing by its own hands, leaving it in the dust of more cooperative societies. If stealing was common, property would essentially become meaningless, making it so that the most audacious thieves are the pinnacle of society, or simply increase bitterness, conflict, and outright violence over the unfairness involved, weakening the cohesion of the group. Adultery leads to unclear paternity and, if done secretly, is a betrayal of a mate's trust that could result in group separation or outright retaliation. Interestingly, rape and slavery have no such easy refutations on such a simplistic level (which may account for the fact that they are not rebuked by the Bible...). But, it is fairly easy to see, if not in the midst of a hypothetical social group, but purely within the realm of reason, that rape is cruel and unfair to victim, due to it causing physical harm and being undesired by the victim, along with its potential for psychological harm, and slavery is simple economic and social injustice, even if there is actually no social ramifications for the group enslaving others.
With the combination of pure reason, one can easily come up with objective moral standards, and, with the combination of human empathy, emotion, and experience, develop subjective, individual moral standards as well. Of course, when it comes down it, it is difficult to say what universal morals exist with such a method, because universal morality derived from logic and basic group dynamics alone are just as likely to be ignored as the morality supposedly imposed upon us by God. So, all in all, it really is incredibly difficult to pin down an answer, making this (drumroll please) an epic waste of time and energy!
But, hey...that's my life...