  Moore’s open question argument can be regarded as giving form to this intuition. If the moral property of being good, for instance, could be defined in wholly psychological, biological, or sociological terms, then moral truths would turn out to be either psychological, biological or sociological truths, which could then be discovered by empirical research by the appropriate science. But, Moore argues, all such definitions must fail, for it is always an open question whether the thing that has the relevant empirical property is good. Moore’s argument can be captured as follows: