What is the future of causal models of cosmic structure formation?
  Recent research has severely constrained the standard ``defect'' models of cosmic structure formation. Here I discuss the nature of the problems with defect models, and place this discussion in the context of the big picture of cosmic structure formation. In particular, I classify models of cosmic structure formation as either ``causal'' or ``acausal'', and ask whether the problems with the defect models extend to all other causal models. I argue that determining the causal nature of the primordial perturbations is within the reach of modern cosmology, and that such a determination would yield deep insights into the very early Universe. 
Andreas Albrecht (Imperial College)