The Extended Mind by Andy Clark and David Chalmers (1998) is a seminal work in the field of extended cognition. In this paper, later a 🏷️#book, Clark and Chalmers present the idea of active externalism (similar to semantic or "content" externalism), in which objects within the environment function as a part of the mind. They argue that it is arbitrary to say that the mind is contained only within the boundaries of the skull. The separation between the mind, the body, and the environment is seen as an unprincipled distinction. Because external objects play a significant role in aiding cognitive processes, the mind and the environment act as a "coupled system".
The Extended Mind was recommended to me by 📝Justin Lane, PhD.