Earlier quoted context omitted.
The free market can only work if everybody had perfect information and no secrets. Otherwise whoever has more information can manipulate reality.
Perfect information and unlimited computing power.
In particular, relevant to this thread, if you have a magical CSV file created by an Oracle associating every food available in US with how "healthy" they are and how much calory they provide, in order to build a 2500 calory diet that maximizes health and minimizes cost, you need to solve a knapsack-like problem. In this environment market will necessarily be a little random not because we don't have enough information but because we don't have enough computational power.