The paper is concerned with the role of uncertainty in an economy undergoing an economic transition. We aim especially at the uncertainty of the Keynesian type. First, a framework for classifying different views on uncertainty is constructed based on literature dedicated to various types of uncertainty. We define risk, as it is commonly adopted in the mainstream economics and uncertainty, outlined by Knight and Keynes and worked up by the Post Keynesians, although for mainstream approach these two concepts are synonymous. This framework is subsequently applied on two cases of decision-making, which appeared during the transition process in the Czech Republic. We show that some important phenomena in Czechia in the 1990s took place under conditions of fundamental or ontological uncertainty. In particular, it was the voucher privatization and Tosovsky dilemma that fit the definition formulated before. Further, potential recommendations for economic policy emerging from the presence of uncertainty are outlined, and their aptness for the Czech transition process is evaluated. We demonstrate that certain outcomes could have been significantly better had the Czech government taken the aspect of uncertainty into account. Hence, we give real-life reasons for fundamental uncertainty being taken seriously and incorporated into economic theory or at least economic policy.