You Cannot Logically Derive Ought From Is

Following Hume, you cannot derive an 'ought' from an 'is': by the rules of deductive logic, garbage in/garbage out, values in/values out, facts in/facts out—you cannot derive normative conclusions about what is morally right without including in your premises an assumption or axiom that relates to values; this is a straightforward computational/logical claim that everyone should accept, independent of the separate question of moral realism.