This paper explores the semantic-pragmatic functions of the Korean causal connective –nikka. It has been widely observed that because-clauses are ambiguous depending on the level of causation: propositional, epistemic, and speech-act level causations. (e.g. Sweetser 1990) Many researchers argue that Korean also has three level causations and the two Korean causal connectives, -nikka and –ese ‘because’, are used in different levels of causation: while the usage of –ese is restricted to a propositional level causation, -nikka can be used in epistemic or speech-act level causations, as well as propositional level causations. I argue, departing from previous analyses, that the three different levels of causation do not exist in Korean. Alternatively, I propose that a nikka-clause always targets a propositional argument. Under this point of view, it is assumed that a nikka-clause takes a mood marked phrase: [ϕ-nikka [Mood(φ)]. On the basis of this structure, I argue that the various function of the nikka-clause results from the different types of mood in the main clause.