The philosophical problem of the tension between liberty and order has dominated the agenda of western philosophy and social science circles since the beginning of the history of thought, and it is a leading issue nowadays, too. The problem of the act of decision is particularly one of the significant themes of contemporary political thought. Instead of the classical poles of both voluntarism and determinism prioritising either the subject or the structure, what should be employed is a much deeper analysis of the relation between undecidability and the act of decision. On this issue, the discussion between Ernesto Laclau and Slavoj Zizek is considerably illuminating. But there are also theoretical shortcomings shared by those thinkers. That is, despite the informativeness of this debate, there is an overwhelming necessity to critically assess this dialogue with a particular emphasis on the conceptual issues. In this regard, an overall scrutiny and critical assessment of this debate constitute the main body of this work.