According to functionalism, for a system s to instantiate a mental property M is for s to: a. Be in an internal state which stands in appropriate causal/functional relations to sensory inputs and other internal states, irrespective of its relations to behavioural outputs. b. Be in an internal state which stands in appropriate causal/functional relations to other internal states and behavioural outputs, irrespective of its relations to sensory inputs. c. Be in an internal state which stands in appropriate causal/functional relations to sensory inputs and behavioural outputs, irrespective of its relations to other internal states. d. Be in an internal state which stands in appropriate causal/functional relations to sensory inputs, other internal states, and behavioural outputs.