Imagine a person who always, in every circumstance, makes rational decisions with his money. He saves when he ought to and spends exactly as he should spend, in order to maximize the “utility” of whatever wealth he happens to possess. He defers gratification with ease. When he invests, he has instant and total access to all possible information related to every item in his, including the details of every company’s financials and any impactful world events, even if they haven’t reached the news media yet. If he found a $100 bill on the sidewalk, he would immediately go out and invest it in a steel mill.