That's a false dichotomy. In natural law theory, the "ought" proceeds from the "is". The good of a thing is determined by its nature. Thus, we eat food because

That's a false dichotomy. In natural law theory, the "ought" proceeds from the "is". The good of a thing is determined by its nature. Thus, we eat food because it IS good for us to do so and we OUGHT to do what is good. A thing's excellence is teleological. In other words, is/ought is only a problem in a materialistic/Cartesian metaphysics. A hylomorphic metaphysics, on the other hand, has no problems with this. I encourage reading Aquinas and Aristotle to this effect. We've been brain damaged by a very crude worldview taught in schools that must be confronted and undone. So given that, while empirical science doesn't determine moral truths per se, it can give enrich out understanding to permit us to make moral determinations. A good example is fetal development. Before science was able to know how prenatal human life begins and develops exactly, the accepted theory in the West held that the human organism comes into being 40 days after fertilization. However, we now know that the human organism comes into being at the moment of fertilization. This fact has moral consequences and we must adjust our moral judgements and actions accordingly.