John Rawls, in his seminal work 'A Theory of Justice,' does not explicitly justify 'discrimination' in the common negative sense of unfair or prejudicial treatment. Instead, he introduces a concept that allows for certain inequalities in the distribution of social and economic goods, provided these inequalities ultimately serve to benefit the least advantaged members of society. This is known as the Difference Principle, and it can be interpreted as a form of 'differential treatment' rather than 'discrimination' in its pejorative sense, aimed at achieving a more just outcome.

Rawls's theory is built upon the idea of a hypothetical 'Original Position' where individuals, behind a 'Veil of Ignorance,' choose the principles of justice that will govern their society. Behind this veil, they are unaware of their own social status, talents, beliefs, or any other particular characteristics. This ensures impartiality in the selection of principles.

From this Original Position, Rawls argues that rational individuals would choose two principles of justice:

1. The First Principle (Liberty Principle): Each person is to have an equal right to the most extensive scheme of equal basic liberties compatible with a similar scheme of liberties for others. This principle ensures fundamental civil and political rights for all.
2. The Second Principle (Difference Principle and Fair Equality of Opportunity): Social and economic inequalities are to be arranged so that they are both:
   • (a) To the greatest benefit of the least advantaged (the Difference Principle).
   • (b) Attached to offices and positions open to all under conditions of fair equality of opportunity.

It is the Difference Principle that addresses the question of 'discrimination' or differential treatment. Rawls acknowledges that a perfectly equal distribution of all goods might not always be the most just or efficient. He argues that certain inequalities – for example, higher salaries for doctors or innovators – can be justified if they incentivize individuals to develop skills or take on roles that ultimately produce greater benefits for everyone, especially those at the bottom of the social ladder. For instance, if a higher salary for a doctor encourages more people to become doctors, leading to better healthcare for the entire population, including the poor, then this inequality is just.

Therefore, Rawls's 'justification of discrimination' is not about favoring one group over another arbitrarily, but rather about allowing for structured inequalities in social and economic arrangements only if they demonstrably improve the prospects of the worst-off. This is a form of positive discrimination or affirmative action in a broad sense, where differential treatment (e.g., progressive taxation, social welfare programs, or even targeted educational support) is employed to level the playing field and ensure that the benefits of societal cooperation are distributed in a way that prioritizes the most vulnerable. It's a move away from strict equality of outcome towards an equality of opportunity that is sensitive to the needs of the least advantaged, ensuring that no one is left behind in the pursuit of collective prosperity.