Equality can be seen as the defining feature of socialist ideology. It is the political value which contributes to the uniqueness of socialism compared to its rivals. Socialist egalitarianism is characterised by a belief in equality of outcome. There a number of arguments for why socialists favour this:

Social equality upholds principles of justice and fairness
Socialists avoid explaining the differences in wealth between people in terms of innate variation in the abilities of individuals
The largest forms of human inequality are seen as a result of unequal treatment in society

Justice demands that people are treated equally. Socialists argue that formal inequality is insufficient politically and legally, as it disregards structural inequalities that exist in the capitalist system. Moreover, equality of opportunity creates a myth of natural inequality in order to legitimise the inequalities that exists within society.

Ultimately, social inequality underpins values of community and cooperation. If people identify with each other as equals they are more likely to work together for the common good. Therefore, equal outcomes strengthen cohesion and solidarity within society.