Markets have come to form one of the most important of all social institutions. In attempting to evaluate the functioning of markets, a significant issue is of the extent to which their justification as an ideal is also capable of providing support for their actual ongoing functioning. In this way, the assessment of market interaction seems to face one of the prominent themes of contemporary political philosophy: what value can be derived from theoretical endeavours that function at a high level of generality and abstraction when it comes to providing guidance within the messy reality of social life? Or, more briefly, how useful is ideal theory within nonideal circumstances?This thesis proceeds, via a specific focus upon labour markets informed by the Rawlsian ideal of justice as fairness, to give a response to the above question. It rejects strong critiques of ideal theory, arguing that theoretical ideals remain able to provide direction to social reform, as they help to define the goals that such reform ought to aim for. However, the thesis argues that additional work may be required to supplement an abstract ideal, if guidance is required about specific elements of social life in nonideal circumstances. Via a focus upon moral psychology, it argues that theorists must attempt to understand why people subscribe to particular practices and what may be of value within them that efforts at reform may want to preserve.In specific relation to labour markets, the thesis develops an understanding of both the gains and threats that accompany their operation. It draws particular attention to recent developments within productive processes that have seen a move towards greater flexibility in working practices. The thesis argues that, from a Rawlsian perspective, there are good reasons to endorse some measure of market activity. However, as this endorsement remains conditional upon the fairness of background conditions, the thesis also demonstrates how efforts and reform may best proceed where these background requirements are absent. By demonstrating what is of value within labour market processes, it offers an outline of a range potential reforms - some of a more ideal nature, some of a more practical nature - that are consistent with the aims of justice as fairness.