I am doing a research paper on Greek Mythology, and I am having trouble coming up with a thesis.?

I chose my topic, then I found out that the paper has to be argumentative/persuaasive in nature. This makes matters a bit harder. I need a hypothesis...I have no clue what I should hypothesize about. I planned on just simply researching Greek Mythology and talking about it, however that isn't acceptable. Please someone help me. The best that I have come up with is: Greek Mythology is the basis for modern religions. My teacher said it was okay, however I hate it. I want to find something that stays with in the confines of Greek Mythology. I do not want to cloud it up with other forms of religion.