It's April 20th, known the world over as International Pot Smoking Day. If you're reading this you're probably not stoned. Although given the increasingly numerous reasons to be stoned, you very well might be.

No longer advocated purely by groups like High Times and NORML—which has a membership special of, you guessed it, $4.20 today—the free and groovy use of marijuana is experiencing a bit of a vogue lately. Ron Paul and Barney Frank have made statements in support of legalization. Twelve states have legalization proposals in their legislatures at the moment. Attorney General Eric Holder said he will not enforce Bush-era strictures against medical marijuana use. Observers of the Mexican narco war have said legalization could go a long way toward easing the violence.

A lot of Big Think guests have discovered themselves at the north end of a bong, but now that it's de rigeur to ask personal positions on marijuana, we've become more curious. Carl Hart, Associate Professor of Psychology at Columbia, told us marijuana legalization is a layered issue when we spoke with him recently.

Pros and cons must be weighed if legalization is to be considered seriously, he said. Do we want marijuana to reach the levels of popular use that alcohol has? Or is it better to spend billions on largely failed drug policies and enforcement? "You will have problems either way," Hart said "but the point becomes which problems are we willing to tolerate as a society."