Utilitarianism is not concerned with persons. It only considers the sum of pleasure and pain in the world. It therefore treats persons as replaceable. One person's increased pleasure is worth another's increased pain. Nordin questions the possibility of weighing these feelings between people on theoretical as well as practical grounds.
Utilitarianism can have seemingly absurd consequences.
A common example is gladiator games, which make a lot of people somewhat happier by harming a few persons. Also, it is a hedonistic imperative to increase the population on earth as much as possible, since even a marginally happy life will add to the total happiness. This pretty much covers the main objections against utilitarianism. I will examine them one by one. This argument that we cannot compare pain between individuals has a theoretical and a practical part.