The kinds of entities that can be described as causing an event depend, in part, on the language one speaks. Whereas in English and Chinese it is possible to say The knife cut the bread or The key opened the door, in Korean and many other languages, such sentences sound very odd. According to the initiator hypothesis, languages fall into two major groups with respect to possible external arguments in causal expressions: those that require that the causer be capable of generating its own energy and those that require only that the causer participate in the causal chain leading up to a particular result. In support of this hypothesis, we show that ability to self-energize has a larger impact on acceptability ratings in Korean than in either English or Chinese (Exp. 1). We also show that restrictions on possible causers extend to the semantics of possible causes in the descriptions of animations depicting causal chains (Exp. 2). Finally, we show that cross-linguistic differences in the linguistic coding of causers may have consequences for the way people conceptualize animations of causal chains in terms of number of events (Exp. 3). Implications for the representation of verb meaning and the semantics of external arguments in other languages are discussed.