“It’s not that he was wrong to have great ambitions. Alexander just never grasped Aristotle’s “golden mean”—that is, the middle ground. Repeatedly, Aristotle speaks of virtue and excellence as points along a spectrum. Courage, for instance, lies between cowardice on one end and recklessness on the other. Generosity, which we all admire, must stop short of either profligacy and parsimony in order to be of any use. Where the line—this golden mean—is can be difficult to tell, but without finding it, we risk dangerous extremes. This is why it is so hard to be excellent, Aristotle wrote. “In each case, it is hard work to find the intermediate; for instance, not everyone, but only one who knows, finds the midpoint in a circle.”