Dr. Sean Carroll is Homewood Professor of Natural Philosophy — in effect, a joint appointment between physics and philosophy — at Johns Hopkins University in Baltimore, and fractal faculty at the Santa Fe Institute. Most of his career has been spent doing research on cosmology, field theory, and gravitation, looking at topics such as dark matter and dark energy, modified gravity, topological defects, extra dimensions, and violations of fundamental symmetries. These days, his focus has shifted to more foundational questions, both in quantum mechanics (origin of probability, emergence of space and time) and statistical mechanics (entropy and the arrow of time, emergence and causation, dynamics of complexity), bringing a more philosophical dimension to his work.