It requires no substantiation, it is in the common definition of social utility that each persons contribution to it should have a priori equal weight.
You say by DEFINITION of social utility everyone's contribution should have equal weight?
Are you saying the fat lazy guy sitting on his arse eating cheetos and playing viddeo games have as much value to society as the cardiac surgeon working 14 hours a day and saving several lives per week ?
Why would you bring such a terrible statement ?
I honestly hope you are trolling, because if you normalise such bs in your own mind, you are harming yourself - programming your own mind to accept bad ideas as normal, training it to make bad decisions in all areas of your life if you are not very careful.
PS: WHO's definition of social utlity are you using, and why are you uncritically imbibing it ?
