 The distribution of material goods and services is not the only economic distribution which is important to people. The distribution of opportunities is also important. As noted in the previous section, John Rawls conjoined his Difference Principle with a principle of equality of opportunity. Endorsement of some form of equality of opportunity is very prevalent among distributive justice theorists and, indeed, among the general population, especially when combined with some form of market distributive mechanism. Equality of opportunity is often contrasted favorably with ‘equality of outcome’ or strict egalitarianism, by those who believe that we can show equal concern, respect, or treatment of people without them having the same material goods and services, so long as they have equal economic opportunities. An equality of opportunity principle then, is combined with other principles to ensure that the inequalities permitted by the overall theory (whether utilitarian, desert, or a Rawlsian difference principle) are only justified if people have the relevant kind of equal opportunity to achieve greater or lesser amounts of goods. So an equality of opportunity principle allows those theorists who depart from strict equality to capture some of what nonetheless has motivated egalitarians. What is the morally best interpretation of this equality of opportunity principle has been a significant focus of research (see  Equality of Opportunity),  particularly among luck egalitarians. In fact, the luck egalitarian ideal (also sometimes known as the ‘level playing field’ ideal) elevates the role of equal opportunity to the central distributive ideal, so that distributive inequalities are only just when they flow from one’s choices or from factors for which one can reasonably be held responsible.