Natural law theory was originally formulated and developed by the Stoic and Aristotelian philosophers of ancient Greece. It was part of a grand cosmological system or scheme of universal order...

Natural law theory was originally formulated and developed by the Stoic and Aristotelian philosophers of ancient Greece. It was part of a grand cosmological system or scheme of universal order according to which facts and values are deeply intertwined and everything in nature has a special virtue or essence, purpose, and place. Such a world-view seems quaint and fanciful today and has been effectively dismantled by modern science (which, among other things, no longer supports the notion of atelos– i.e., a strategic goal or purpose – in the events and structure of the natural world.) However, this has not prevented modern-day proponents of Natural Law theory from attempting to extend and justify the theory, and consequently there are still philosophers and theologians who try to ground morality either on known or presumed facts about human nature or on truths that seem evident to practical reason. But is it self-evident or reasonable to say, as Natural Law proponents have claimed, that abortion, suicide, contraception, and same-sex relationships are wrong? Is it possible to deduce moral rules from facts about human nature? In short, is Natural Law theory still a viable and credible moral theory today?