As suggested, I try asking this question in the biology forum. https://www.physicsforums.com/showthread.php?t=45269 I know that there are different pathways in the brain for pleasure and pain. But at some point these must connect in order to make a decision. So from a biological point of view, is it possible to avoid the feeling of pain? Or would any kind of diminishing of reward feel as pain for a higher form of life? Or if possible to have a system based only on pleasure, would this be inferior to a system based both on pleasure and pain?