 The probability associated with any foundational claim must be understood as a blind posit, i.e. as a good guess, which according to Reichenbach can take into account pragmatic considerations. Thus, Reichenbach posits the existence of the external world as he thought it would make causal laws more “homogenous” (1938c). In a rather mixed metaphor, Reichenbach compares our knowledge of the external world to seeing shadows of flying birds on the walls of a cube in which one is confined. He argues that the patterns on the walls, their regularity, would result in a high probability that there are objects outside the cube producing the shadows. 