Can you help me recall a phrase about economic theory?

Some time ago, I read in an article about the recent financial meltdown that a theory had emerged in the 1970s. It was originally pushed by Milton Friedman and became prevalent with what came to be known as the Chicago school of economic theory. It stated that sufficiently free markets always value every investment perfectly—and that things only get assigned incorrect values, leading to boom and bust economies—when governments control markets and not just monetary policy.

The idea was called something like “market excellence” or “market perfection” but I can’t recall just what words were paired together nor can I find it taking wild stabs on Google. Can anyone help me recall the term or point me to a source?