(November 16, 2009) Leonard Susskind discusses the theory and mathematics of particle spin and half spin, the Dirac equation, and isotopic spin. Leonard Susskind, Felix Bloch Professor of Physics, received a PhD from Cornell University and has taught at Stanford since 1979. He has won both the Pregel Award from the New York Academy of Science and the J.J. Sakurai Prize in theoretical particle physics. He is also a member of the National Academy of Sciences. Stanford University: www.stanford.edu/ Stanford Continuing Studies Program csp.stanford.edu/ Stanford University Channel on YouTube: www.youtube.com/stanford