Excess Baggage
  Many advances in physics have in common that some idea which was previously accepted as fundamental, general, and inescapable was subsequently seen to be consequent, special, and dispensable. The idea was not truly a general feature of the world, but only perceived to be general because of our special place in the universe and the limited range of our experience. It was excess baggage which had to be jettisoned to reach a more a more general perspective. This article discusses excess baggage from the perspective of quantum cosmology which aims at a theory of the universe's quantum initial state. We seek to answer the question `Which features of our current theoretical framework are fundamental and which reflect our special position in the universe or its special initial condition?' Past instances of cosmological excess baggage are reviewed such as the idea that the Earth was at the center of the universe or that the second law of thermodynamics was fundamental. Examples of excess baggage in our current understanding of quantum cosmology are the notion that measurement is central to formulating quantum mechanics, a fundamental quantum mechanical arrow of time, and the idea that a preferred time is needed to formulate quantum theory. We speculate on candidates for future excess baggage. (This article appeared in 1991 but is posted here for accessibility and possible current interest.) 
James B. Hartle