The default assumption of standard economics is to treat preferences as exogenously "given", consistent with one another, "revealed" by past choices, and context independent. There has been increased interest recently (within behavioural economics) in the impact of inconsistent or irrational preferences and (more broadly) in dynamic and endogenous preferences. This paper builds on these challenges to standard assumptions by analysing the pivotal role of three aspects of preference formation in explaining capitalist dynamics and market instability. These are the constant creation of new preferences and the indeterminacy of choice sets in the context of widespread product innovation; the moral indeterminacy implied by conflicting and incommensurable social norms attaching to market goods where there is no single scale of value and hence no unique set of rational trade-offs; and, lastly, the contingent social and market construction of the product differentiation, quality attribution, and value assessments central to preference formation. The paper concludes by considering implications for economics as a discipline.