Chaos provides a link between determinism and randomness. It demonstrates that even very simple systems are capable of random behavior, and that randomness does not necessarily depend on the complexity of initial data. Instead, nonlinear geometrical relationships in the laws of motion cause mixing of nearby initial conditions, so that the states of the system are shuffled, much like a deck of cards. Even though the geometric relationships dictated by the laws of motion may be quite simple, the resulting trajectories can be highly complex. Small changes in initial conditions are amplified into very large changes in long-term behavior, making the relationship between cause and effect so complicated as to be effectively random. This complexity is generated internally, rather than externally. From any practical point of view the result is random
Eubank, S. & Farmer, J.D (1989). 'An Introduction to Chaos and Randomness'. In 1989 Lectures in the Sciences of Complexity, ed. E. Jen. Santa Fe Institute Studies in the Sciences of Complexity, Lect. Vol. II. Redwood City, CA: Addison-Wesley.