Here is the argument: From a neuroscientific outlook, when brain produces any of these six hormones of Endorphins, Dopamine, Oxytocin, Norepinephrine, Cortisol and Adrenaline, one feels pleasure.
So if someone is in a state of total inactivity, and thinks about nothing pleasurable or troubling and feels no pain in his body, the reward system of the brain is not working*. So it does not produce any hormones that create such effect which is generally known as pleasure.
I'm as much a biologist as I am a fridge but if none of the hormones and neurotransmitters are at work at any given time in one's body, wouldn't that be a strong indication that this individual is as alive as a dodo?