For a long time, philosophers have made the case for God's existence based upon a moral argument. Rationally-minded atheists have countered by saying that one can be good without believing in God. And that's true — one can act in a way that most of us find morally praiseworthy without believe in God. You just can't explain why.
Here's the point: the rational sciences are quite good at making "is" statements. Light is both a particle and a wave. Water is two parts hydrogen and one part oxygen. Eating a pound of bacon a day is bad for your health (but really delicious).
But rationality alone can't take you from "is" to "ought." Just because we can scientifically demonstrate that eating the aforementioned daily pound of bacon will have deleterious effects on your heath doesn't mean you ought not do it. In order to believe you ought not do that you must first have some pretty strong beliefs (on faith) about human nature, its value, and that living a long time is more morally praiseworthy than choosing to die and early death for the love of pork products. In other words, you need more than mere rationality.
Alvin Plantinga warns us against placing all our epistemological eggs in the basket of the rational sciences, saying:
Some treat science as if it were a sort of infallible oracle ... Many look to scientists for guidance on matters outside of science, matters on which scientists have no special expertise. They apparently think of scientists as the new priestly class; unsurprisingly, scientists don't ordinarily discourage this tendency. (1)
Before your take all your oughts from the "sciences," do a little thought experiment with me ... if you're brave enough to be unsettled. Ask yourself, what are those "ought" statements that you believe so strongly? Now ask yourself what beliefs you have to believe to believe so strongly in those statements?
Where do those strong beliefs come from?
At the end of that chain of reasoning, you might find yourself standing next to God. Which isn't a bad place to start figuring out the "oughts" of life.
(1) Alvin Plantinga, Where the Conflict Really Lies: Science, Religion, and Naturalism (Oxford, 2011) 18.