The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage.By Nathan Slaughter NEW YORK ( StreetAuthority) -- Despite what any financial academic or index fund advocate tells you, the market isn't perfectly rational. If it were, then it would be impossible to identify a stock that is meaningfully undervalued. There would literally be no way for an active stock picker to beat the market -- other than blind luck. But, as I was saying, that's not the case. The market is good, but it's not perfect. It makes mistakes. And we should all be thankful for that. Otherwise, there'd never be any exceptional buys. You can't get ahead by paying full price all the time. And we only get to buy stocks at attractive discounts of 50% or more because the market goofs up from time to time.