Functionalism posits that mental states are determined by

• A. Physical properties
• B. Functional properties
• C. Behavioral outputs only
• D. Genetic makeup

Answer: (B)

Mental states are defined by what they do in the system—their functional roles. In functionalism, a mental state is identified by its causal relations: what causes it, what it produces, and how it relates to other mental states and inputs. This means a state like pain is characterized by its function: it arises from injury, it tends to drive avoidance or protective behavior, it accompanies reports of pain, and it connects with beliefs and desires about the injury. The key point is that this functional role can be realized in multiple ways, across different physical substrates, as long as the same causal pattern holds.

Because of that, mental states aren’t determined solely by their physical properties, nor by observable behavior alone, nor by genetic makeup. A system could implement the same functional relationships even with a different underlying hardware, which is why the functional properties best capture what the mental state is.