In this argument “X is good” would have one meaning in premise (i)—in which it would be an optative—and another in premise (ii)—in which it would be a creature of some other semantic kind. (I have emphasized the point by putting the first occurrence in italics and the second in bold.) But an argument is only valid if the words involved retain the same meanings throughout the inference. If not, we have an instance of the fallacy of equivocation. So it looks as if any attempt to deal with Geach’s