Functionalism states it the function of something which defines something as what it is. Whatever it may be, everything is defined by its function. In terms of it inputs and outputs for a given function is what defines something as being itself. It is the function that is absolutely important. For example a kidney has a function and its function is what makes it a kidney. The kidney receives blood as an input and produces urea with filtered blood as an output. This is its function. In the same way an artificial kidney has the same function and so can still be regarded as a kidney. It has different properties; it is larger, made of plastic and metal. It has completely different “engineering” but its function remains the same. This defines it as a kidney. Because of this view from functionalism it allows this theory to overcome problems of many other materialist theories, hard behaviourism in particular.
Functionalism is an advance on hard behaviourism as behaviourism states there is only objective behaviour; this is all there is to behaviour. It is actions as that is all we can empirically observe. For example hard behaviourists would state if we can see someone crying, all we can observe is their behaviour of crying, the tears leaving the eye and running down this person’s miserable face. There are no mental states and nothing happening in-between the thing that makes the person cry and saline tears being secreted from the tear duct.
Behaviourism does not explain the place between a person’s mental states or “beliefs” before a behaviour is exacted. Behaviour is simply the way in which we act. Behaviour therefore is just simply the way we act. Returning to our tear example, it is merely production of saline liquid from a tear duct that implicates sadness. This is a problem as it does not acknowledge any interactions between how we feel or our “mental states” before