In this paper, we address the problem of how people understand predicative metaphors such as ``The rumor flew through the office,'' and argue that predicative metaphors are understood as indirect categorizations. In the indirect categorization process, the verb (e.g., fly) of a predicative metaphor evokes an intermediate entity, which in turn evokes a metaphoric category of actions or states (e.g., ``to spread rapidly and soon disappear'') to be attributed to the target noun (e.g., rumor), rather than directly creating a metaphoric category as argued by Glucksberg's (2001) categorization theory. We test our argument using two experiments, offline comprehension and online priming. The two experiments provided convergent evidence for our argument. The psychological validity of indirect categorization as a process of predicative metaphor comprehension was confirmed.