In this lecture, Juan Maldacena, Professor in the School of Natural Sciences, describes the theoretical ideas, developed in the 1960s and '70s, that led to the prediction of the Higgs boson, the particle that appears to have been discovered over the summer in 2012. The forces of nature are based on beautiful symmetries. Maldacena explains why the Higgs mechanism is necessary to avoid some of the naive consequences of these symmetries and to explain various features of elementary particles.