Equality of opportunity is to be contrasted with equality of outcome. While advocacy of the latter has been traditionally associated with a left-wing political philosophy, the former has been championed by conservative political philosophy. Equality of outcome fails to hold individuals responsible for imprudent actions that may, absent redress, reduce the values of the outcomes they enjoy, or for wise actions that would raise the value of the outcomes above the levels of others’. Equality of opportunity, in contrast, ‘levels the playing field,’ so that all have the potential to achieve the same outcomes; whether or not, in the event, they do, depends upon individual choice.
A brief, clear introduction to the topic. But for those who want to delve deeper, I recommend his recent paper (with Gary Fields, V. Dardononi and L. Sanchez) How demanding should equality of opportunity be, and how much have we achieved? (PDF). It applies his ideas to several datasets, to compute what kinds of equal opportunity have been achieved in the US and the UK:
This paper proposes tests of various notions of equality of opportunity and applies them to intergenerational income data for the United States and Britain. Equality of opportunity holds if the chances that individuals have to succeed depend only on their own efforts and not upon extraneous circumstances that may inhibit or expand those chances. Exactly what “effort” and “circumstances” should include is a contentious issue.
We discuss four channels through which parents affect the income earning capacities of their children: provision of social connections, formation of beliefs and skills in children through family culture and investment, genetic transmission of native ability, and instillation of preferences and aspirations in children. We test for equality of opportunity using ever more stringent definitions and find only the weakest of support in the United States and no support at all in Britain.