It is generally assumed by science that the physical world is causally closed, in other words that consciousness has no causal effect on human behaviour, and that 'intentional' human action is an illusion caused by physically deterministic (mindless) processes in the brain. In other words that there is no such thing as free will. However if mind is caused by brain then all states of consciousness have a neural correlate, a matching brain state. In this case how is it possible to distinguish between conscious intentional action and mindless physical cause and effect? They would both look exactly the same. If it is not possible to distinguish between them then on what grounds can evolutionists be so sure that conscious choice and purposeful (teleological) action have no role in the evolution of species?