Free will as relative freedom with conscious component.

The general notion of relative freedom is introduced. It is a kind of freedom that is observed everywhere in nature. In biology, incomplete knowledge is defined for all organisms. They cope with the problem by Popper's trial-and-error processes. One source of their success is the relative freedom of choice from the basic option ranges: mutations, motions and neuron connections. After the conjecture is adopted that communicability can be used as a criterion of consciousness, free will is defined as a conscious version of relative freedom. The resulting notion is logically self-consistent and it describes an observable phenomenon that agrees with our experience.