When this recognition of difference was put together with the clear understanding that Creatura was organized into circular trains of causation, like those that had been described by cybernetics, and that it was organized in multiple levels of logical typing, I had a series of ideas all working together to enable me to think systematically about mental process as differentiated from simple physical or mechanistic sequences, without thinking in terms of two separate "substances." My book Mind and Nature: A Necessary Unity combined these ideas with the recognition that mental process and biological evolution are necessarily alike in these Creatural characteristics.

Gregory Bateson, Angels Fear