The Pareto condition (or Pareto optimality) is a criterion from welfare economics: a state of affairs is Pareto optimal if no one can be made better off without making someone else worse off. A change is a Pareto improvement if it benefits at least one person while harming no one.
The concept, named after Vilfredo Pareto, serves as a minimal criterion of efficiency in economics and social choice theory. Its appeal lies in requiring no interpersonal comparisons of utility — it does not ask how much better or worse off anyone is, only whether someone gains and no one loses. This makes it formally clean but substantively weak: a distribution where one person holds everything and everyone else has nothing can be Pareto optimal, because any redistribution would make the one person worse off.
In political philosophy, the Pareto condition figures in debates about the relationship between efficiency and justice. Libertarians (Robert Nozick) appeal to it to argue against redistribution; critics note that Pareto optimality is compatible with extreme inequality and says nothing about the justice of the initial distribution. The Pareto condition illustrates a general pattern: formal criteria that avoid substantive commitments do not thereby achieve neutrality — they encode the status quo as a baseline.