Under normal viewing conditions, the slightly different images projected onto the back of the two eyes fuse to give the perception of depth. When the images falling on corresponding areas of the retina are so different as to be incompatible, binocular rivalry (BR) occurs. This involves a conscious alternation in perception of the two different images, with one dominant and the other suppressed at a given point in time. Because the physical input to the two eyes remains constant, rivalry provides an intriguing case study of how the brain ‘makes up its mind’  when faced with conflicting information. The new edited book by David Alais and Randolph Blake provides an excellent overview of the current state of research on BR, and places it within its historical context.