Noam Chomsky has said, "As soon as questions of will or decision or reason or choice of action arise, human science is at a loss." Today we're examining the physics of ideas -- how and why we make the decisions we do. Sociologist and physician Nicholas Christakis discusses how social networks shape our choices, and ultimately our lives. John Cookson examines the neurological basis of decision-making, and Supreme Court justice Stephen Breyer fields the perennial question: "Does public opinion influence the judicial decisions?" Maria Konnikova argues that we can take a few pages from Sherlock Holmes' playbook to better understand our considerations.