I like W.D. Ross’s mixed deontology of irreducible prima facie duties, like keeping promises and repaying debts and exercising beneficence. Ross takes these duties to be self-evident and known with certainty, while he acknowledges that we can have no more than “probable opinion” about the rightness of a particular action. He also accepts that the several duties can conflict with each other and that we have no recourse except to use our “judgment” in such cases, with no overarching criterion of rightness to resolve such conflicts. Critics have found these to be weaknesses in his position. I, on the contrary, find them to be strengths. It really is true that the right act is often the fortunate act, and that ascriptions of absolute rightness are hostage to unforseen consequences. Also, it is a philosopher’s illusion to think that there can be any escape from conflicts of principle: moral directives don’t always harmonize and decisions will require the use of context-bound judgment. How can we weigh the wrongness of telling a lie against the potential benefits of lying? There’s no litmus test.