The 18th century Scottish philosopher David Hume famously argued that no description of the way the world is (facts) can tell us how the world ought to be (values). Hume’s argument was actually directed against religious apologists who sought to deduce morality from the existence of God.
Ironically, however, Hume’s reasoning has since become one of the primary causes why some people – mainly of religious persuasion – fail to link morality to human knowledge. In fact, Hume may well have been wrong in his reasoning, since there is strong logical evidence to suggest one can indeed derive an ought from an is.
Axiom 1: There are behaviours, intentions, cultural practices, etc. which potentially lead to the worst possible misery for everyone. There are also behaviours, intentions, cultural practices, etc. which do not, and which, in fact, lead to states of well-being for many sentient creatures, to the degree that well-being is possible in this universe.
Axiom 2: While it may often be difficult in practice, distinguishing between these two sets is possible in principle.
Axiom 3: Our values are ways of thinking about this domain of possibilities. If we value liberty, privacy, benevolence, dignity, freedom of expression, honesty, good manners, the right to own property, etc.—we value these things only in so far as we judge them to be part of the second set of factors conducive to (someone else’s) well-being.
Axiom 4: Values, therefore, are (explicit or implicit) judgements about how the universe works and are themselves facts about our universe (i.e. states of the human brain).
Axiom 5: It is possible to be confused or mistaken about how the universe works. It is, therefore, possible to have the wrong values (i.e. values which lead toward, rather than away from, the worst possible misery for everyone).
Axiom 6: Given that the well-being of humans and animals must depend on states of the world and on states of their brains, and science represents our most systematic means of understanding these states, science can potentially help us avoid the worst possible misery for everyone.