"Planck had slipped the quantum of action into his not fully consistent reasoning. He had, without wholly realizing it, introduced an essential element of discreteness into the description of nature, an element alien to the theories of mechanics and electromagnetism as they then existed. To the young Einstein, however, the imperfections were all too clear... he was hit with a new paradox: Planck was deriving empirically correct equations from hypotheses that contradicted the principles of physics..."