How do you decide whether you ought to do something? Chances are you’ve employed statements about how things are or have been as the basis for making a judgment call. The 18th-century Scottish philosopher David Hume forcefully argued against this approach. According to ‘Hume’s law’, also known as the ‘is/ought problem’, determining what you ought to do based on what is represents a logical mistake because there’s a gap that reason cannot bridge between the facts of the world and the values you might espouse.