func·tion·al·ism 
(fŭngkshə-nə-lĭz′əm)
(fŭngkshə-nə-lĭz′əm)n.
1. The doctrine that the function of an object should determine its design and materials.
2. A doctrine stressing purpose, practicality, and utility.
3. Philosophy The doctrine in the philosophy of mind according to which mental states are defined by their causes and effects.
function·al·ist′ adj. & n.