Functionalism holds that mental states are determined by what they do, rather than by their physical makeup.

• A. Mental states are determined by their functional properties
• B. Mental states are determined by their physical properties
• C. Mental states are determined by social context
• D. Mental concepts are not real

Answer: (A)

Functionalism defines a mental state by what it does—the pattern of causal relations it has to inputs, other mental states, and outputs. In this view, the essential thing about a pain state is the role it plays: it is caused by tissue damage or potential harm, it tends to produce avoidance or withdrawal, it generates beliefs about the need for relief, and it influences behavior accordingly. The physical substrate that realizes this state (brain tissue, or another kind of hardware) isn’t what matters; what matters is the functional role the state plays. That’s why the same mental state can be realized in different physical systems as long as the functional properties match.

So the best answer states that mental states are determined by their functional properties. The alternatives don’t fit because they associate mental states with physical properties, social context, or a claim about the reality of mental concepts, rather than with the function those states perform.