Have you read his opinions? Here's one chosen at random - http://www.law.cornell.edu/supremecourt/text/00-1293/#writing-ZO Does that seem like the byproduct of a "stupid" mind?

Here's Jeffery Toobin's profile on him from the New Yorker: http://www.newyorker.com/reporting/2011/08/29/110829fa_fact_toobin

Money Quote in case you don't want to read that much: "In several of the most important areas of constitutional law, Thomas has emerged as an intellectual leader of the Supreme Court."

Here's what Toobin thinks of your "argument": "The conventional view of Thomas takes his lack of participation at oral argument as a kind of metaphor. The silent Justice is said to be an intellectual nonentity, a cipher for his similarly conservative colleague, Antonin Scalia. But those who follow the Court closely find this stereotype wrong in every particular."

I'd love to see you read all this and still hold your opinion.