Based on empirical evidence we discuss the nature of precognition, and address the questions whether retrocausation/ precognition violates causality, whether precognition implies determinism, the questions of actual or probable futures, from where does the information arise, and other observed properties of precognition. This is followed by a discussion on the primacy of precognition by examining the various categories of psi. In our analysis, precognition is most likely the only form of psi, subsuming within it clairvoyance, telepathy, micro-PK, and the survival (...) hypothesis. In this paper, we examine the various arguments for this assertion, the primary one being that it is impossible to close the precognition door. (shrink)