Thomas is not just a member of the conservative block of Supreme Court justices. He is, without doubt, the most conservative justice, willing to regularly strike down long-accepted case law that has been in place for decades, in some cases for as much as a century.
He is the only justice willing to allow states to establish an official religion; the only justice who believes teenagers have no free speech rights at all; the only justice who believes that it is unconstitutional to require campaign funders to disclose their identity; the only justice who believes that truthful tobacco advertising and other commercial speech may not be regulated, even when it is aimed at minors; the only justice who voted to strike down a key provision of the Voting Rights Act; the only justice to say that the court should invalidate a wide range of laws regulating business; and he is the only justice who voted to allow the president to hold American citizens in prison indefinitely without charge and without review by the courts.
http://www.npr.org/2011/10/11/141213260/thomas-confirmation-hearings-had-ripple-effect?sc=ipad&f=1001