The argument, put simply, goes like this:
- If there is no God there can be no objective moral wrongs, duties or obligations.
- There are objective moral wrongs, duties and obligations.
- Therefore, there is a God.
Those who wish to avoid the conclusion of this argument will often challenge one or both of the premises. They'll argue contra the first premise, for example, that objective moral duties exist independently of God because they result from our evolutionary past, or are derived from human reason or from human conscience.
This short video featuring Boston College philosopher Peter Kreeft considers these and other objections to the Moral Argument and finds them all inadequate. None of them can provide a satisfactory ground for objective moral duties.
The only satisfactory basis for objective moral rights and wrongs is a transcendent, perfectly good moral authority who has the power to hold us accountable for how we live. Here's Kreeft: In other words, if one believes there are objective moral duties but also believes there's no transcendent ground for those duties, there's an intellectual tension in their worldview. One of those beliefs must be false, but it doesn't seem plausible that the first one is.