Cybernetics has an important application in Biology, particularly in explaining how the brain might work. The brain can best be considered as two organs and not one, grey matter and white matter, with different theories to explain the function of each. The current “living transistor theory” seems inadequate to explain the function of neurons which individually appear to feel pleasure and pain and might, therefore, obey some principle of selection of appropriate behaviour similar to that of evolution by natural selection. Finally, any consideration of how the brain treats knowledge demands some clear idea of what knowledge is and how it may be coded in chemical terms.