I would say the utility of a person in a situation S measures how strongly a person prefers that given situation, independently from other possible situations that we could have chosen. But in the end the thing that matters is someone’s relative utility, which can be written as the utility minus a personal critical level. This indeed reframes the discussion into one about where the zero point of utility should lie. In particular, when it comes to interpersonal comparisons of utility or well-being, the utilities are only defined up to an affine transformation, i.e. up to multiplication with a scalar and addition with a constant term. This possible addition of a term basically sets the zero point utility level. I have written more about it here: https://stijnbruers.wordpress.com/2018/07/03/on-the-interpersonal-comparability-of-well-being/

I would say the utility of a person in a situation S measures how strongly a person prefers that given situation, independently from other possible situations that we could have chosen. But in the end the thing that matters is someone’s relative utility, which can be written as the utility minus a personal critical level. This indeed reframes the discussion into one about where the zero point of utility should lie. In particular, when it comes to interpersonal comparisons of utility or well-being, the utilities are only defined up to an affine transformation, i.e. up to multiplication with a scalar and addition with a constant term. This possible addition of a term basically sets the zero point utility level. I have written more about it here: https://stijnbruers.wordpress.com/2018/07/03/on-the-interpersonal-comparability-of-well-being/