 Behaviorism in the philosophy of mind is the view that the mental is nothing over and above behavior (including dispositions to behave). Any version of behaviorism implies that the mental supervenes on behavior. That is: necessarily, two creatures who are behaviorally alike are also mentally alike. Likewise, any version of functionalism or physicalism implies that the mental supervenes on, respectively, functional organization and physical makeup. For the purposes of this subsection, it is not necessary to get into the details of these theories. However, two points should be noted. First, it should not be assumed that either behavior, functional organization, or physical makeup is an intrinsic  matter—the relevant sorts of behavioral, functional, and physical properties may be extrinsic.  In other words, perfect duplicates may differ in behavioral, functional, or physical  respects.[27]  Second, as these theories are usually understood, difference in behavioral respects implies difference in functional respects, which in turn implies difference in physical respects; none of the converse implications  holds.[28]  So the three supervenience theses just mentioned are related as follows: the behaviorist supervenience thesis implies the functionalist thesis, which in turn implies the physicalist thesis.