Conversation so far:
What was Robert Todd Carroll's best known piece of writing?
Robert Todd Carroll was best known for his contributions in the field of skepticism; he achieved notability by publishing The Skeptic's Dictionary online in 1994.
Did Robert Todd Carroll consider himself a writer?
Robert Todd Carroll (May 18, 1945 – August 25, 2016) was an American writer and academic.

Question: What is his idea of a critical thinker?
Self-contained rewrite: What is Robert Todd Carroll's idea of a critical thinker?