The difference principle is a strongly egalitarian conception of justice which evaluates distributions from the standpoint of the least advantaged, such that no improvement in the better‑off’s position counts as a social gain unless it also improves the situation of the worse‑off, and, absent mutually beneficial inequalities, strict equality is preferred.

By John Rawls, from A Theory of Justice

Key Arguments

  • Rawls explicitly characterizes the difference principle as strongly egalitarian: "the difference principle is a strongly egalitarian conception in the sense that unless there is a distribution that makes both persons better off (limiting ourselves to the two-person case for simplicity), an equal distribution is to be preferred."
  • He models indifference curves as right‑angle shapes intersecting the 45° line, representing the fact that increasing one person’s expectations without increasing the other’s yields no gain in justice: "No matter how much either person’s situation is improved, there is no gain from the standpoint of the difference principle unless the other gains also."
  • He assumes X1 as the most favored and X2 as the least advantaged representative person and stipulates that, under the principle, X1’s improvements must be linked to X2’s: "As his expectations are increased so are the prospects of X 2 , the least advantaged man."
  • Rawls notes that perfection of the difference principle corresponds to the point where the contribution curve from the better‑off to the least advantaged is tangent to the highest just indifference curve, capturing the maximin idea: "the difference principle is perfectly satisfied only when the OP curve is just tangent to the highest indifference curve that it touches."

Source Quotes

Assume that indifference curves now represent distributions that are judged equally just. Then the difference principle is a strongly egalitarian conception in the sense that unless there is a distribution that makes both persons better off (limiting ourselves to the two-person case for simplicity), an equal distribution is to be preferred. The indifference curves take the form depicted in figure 5.
The indifference curves take the form depicted in figure 5. These curves are actually made up of vertical and straight lines that intersect at right angles at the 45° line (again supposing an interpersonal and cardinal interpretation of the axes). No matter how much either person’s situation is improved, there is no gain from the standpoint of the difference principle unless the other gains also.
These curves are actually made up of vertical and straight lines that intersect at right angles at the 45° line (again supposing an interpersonal and cardinal interpretation of the axes). No matter how much either person’s situation is improved, there is no gain from the standpoint of the difference principle unless the other gains also. Suppose that X 1 is the most favored representative man in the basic structure.
No matter how much either person’s situation is improved, there is no gain from the standpoint of the difference principle unless the other gains also. Suppose that X 1 is the most favored representative man in the basic structure. As his expectations are increased so are the prospects of X 2 , the least advantaged man. In figure 6 let the curve OP represent the contribution to X 2 ’s expectations made by the greater expectations of X 1 .
Thus the only relevant parts of the indifference curves are those below this line, and for this reason the upper left-hand part of figure 6 is not drawn in. Clearly the difference principle is perfectly satisfied only when the OP curve is just tangent to the highest indifference curve that it touches. In figure 6 this is at the point a.

Key Concepts

  • Assume that indifference curves now represent distributions that are judged equally just. Then the difference principle is a strongly egalitarian conception in the sense that unless there is a distribution that makes both persons better off (limiting ourselves to the two-person case for simplicity), an equal distribution is to be preferred.
  • These curves are actually made up of vertical and straight lines that intersect at right angles at the 45° line
  • No matter how much either person’s situation is improved, there is no gain from the standpoint of the difference principle unless the other gains also.
  • Suppose that X 1 is the most favored representative man in the basic structure. As his expectations are increased so are the prospects of X 2 , the least advantaged man.
  • the difference principle is perfectly satisfied only when the OP curve is just tangent to the highest indifference curve that it touches.

Context

Early in the section 'THE DIFFERENCE PRINCIPLE', Rawls introduces the formal, graphical representation of the difference principle via indifference curves and a contribution curve OP in a two-person diagram, to illustrate its strongly egalitarian structure and maximin focus on the least advantaged.