Written for non-specialists, this book discusses the apparent conflict between relativity and quantum mechanics. The author proposes a resolution based on a causal interpretation introduced by Louis deBroglie and elaborated by David Bohm. He shows that a "medium" or "aether" may be introduced in a manner consistent with both relativity and quantum theory, and which allows the two theories to be unified via the identification of circularly causal processes at their core. While several crucial experiments are discussed in detail, the mathematics is kept simple, making the discussion accessible...