Medium of exchange was observed as early as Oresme, Copernicus and then in 1558 by Sir Thomas Gresham, that bad money drives out good in any marketplace (Gresham's Law states "Where legal tender laws exist, bad money drives out good money"). A more precise definition is this: "A currency that is artificially overvalued by law will drive out of circulation a currency that is artificially undervalued by that law." Gresham's law is therefore a specific application of the general law of price controls. A common explanation is that people will always keep the less adultered, less clipped, sweated, less filed, less trimmed coin,
The Most Good You Can Do Law School professor Eric Posner reviewed the book for "Slate Magazine", concluding: "So what’s an effective altruist to do? The utilitarian imperative to search out and help the people with the highest marginal utility of money around the world is in conflict with our limited knowledge about foreign cultures, which makes it difficult for us to figure out what the worst-off people really need.* For this reason, donations to Little League and other local institutions you are familiar with may not be a bad idea. The most good you can do may turn out to be—not much." Posner wrote a