Moral Philosophy

The other day Jessica had us read a piece she had written on moral philosophy, in which she called a "crash course." In this reading there are some questions posed and some thoughts discussed. I would like to elaborate on the things that I noticed.
First, she poses the question, "what is truth?" I think to the best of one’s knowledge, truth is how people perceive things to be. I wondered how my definition of truth matched up to that of others, and according to answers.com, truth is a statement proven or accepted to be as true. Not an exact match, but similar. Truth is also one of three things. Something believed by the self, something that one chooses to believe that is already set by an authority or religion, or something pushed upon a person by an authority or religion.
This might leave one asking; well what is an authority then. I believe authority to be given to people because they have some knowledge of the topic in question. Someone who has studied or been educated in the topic. Often, that would mean someone who also questions what really could have or did happen, like a philosopher (connection?). Again, according to answers.com, authority is an accepted source of expert information or advice, or power to influence or persuade resulting from knowledge or experience. Similar to my personal definition, but I did not include influencing and persuading people, or giving advice. I did not include these because one does not need to be an authority to give advice, influence, or persuade people. They just have to act like they know what they are talking about.
Next, in the moral philosophy reading Jessica tells of four theories of origin, and asks of our thoughts. These origins are as follows; Divine Command, Natural Law, Culture Realism, and Subjectivism. First, I want to say that in Subjectivism, it is like a five year old mentality. "I like it so it is good." That doesn't solve anything, and it doesn't prove anything. It is just a very immature way of thinking. Second, most Christians and a majority of our culture, including me, believe in Divine Command. I find this interesting because who is to say that Divine Command is more or less corrected than any of the others, and why do they have that authority? I have considered other possibilities recently though, because at this point in my life, I am trying to learn the meaning of life and why I am here.
I feel that this is an interesting topic and may need further exploring by myself in the future, but for now I would like some comments. Thoughts, options, questions, suggestions? Everything is accepted and appreciated. Thank you!
~Elizabeth