Many scholars have looked into relevant problems concerning the usage of causatives in their studies of Classical Chinese grammar. They find that, unlike the derivational system found in most Indo-European languages, the system of word-derivation in Classical Chinese (causative usage included) reveals that certain grammatical and semantic contrasts are regularly associated with tonal contrasts. In spite of such findings, we still consider it rather difficult to separate those derivational causative verbs from the general causative usage to which the syntactic structure is ascribed, not to mention the even harder task of distinguishing the causative usage from the putative one given their similar surface structure. Thus, beside the review and summary of causative usages in previous works, this paper re-analyzes certain problematic cases of causatives using different linguistic factors (i.e., phonological, morphological, and syntactical) together with relevant context clues. Although we have yet to come up with a satisfactory explanation concerning the distinction between causative and putative usages, we maintain that the contrast between realis and irrealis can be employed as a means to clarify those subtle differences in the putative usage.