The causative suffix -kan in Indonesian is often analyzed as a marker of either a benefactive relation or causative relation. The occurrence of suffix in membelikan 'to buy someone something', for example, shows a benefactive relation, while its occurrence in menembakkan 'to shoot something to somebody/something', and menidurkan 'to put somebody to sleep' shows a causative relation.

Though the analysis gives a good account of the different meanings of verbs with the suffix, the analysis fails to explain the relation between sentences whose main difference lies in the presence or absence of the suffix like Rita membelikan Rudi buku 'Rita bought Rudi a book' and Rita membeli buku untuk Rudi 'Rita bought a book for Rudi' and Rita menidurkan Diana 'Rita put Diana to sleep' and Diana tidur 'Diana slept.' The similarity of the pairs of sentences only lies in the root of the verbs. The analysis fails to reveal the syntactic and semantic similarities obviously present in the pairs of sentences.

Another approach to the problem is the adoption of the suffix -kan as an inflection. In the principle and parameter approach, as an inflection, the suffix heads a phrase, called a causative phrase (CsP). Along with the treatment of the suffix as a head of a phrase, the voice affix also heads a phrase (VcP). A verbal sentence in Indonesian is, therefore, a VcP which may take a VP or CsP as its complement. A CsP can also become the complement or adjunct or a VP or another category which becomes the complement of a VcP.

In the analysis, the difference between a causative relation and benefactive relation in a sentence is due to the different functions of a CsP. A CsP shows a causative relation when it becomes the complement of a VcP, and it shows a benefative relation when it becomes the adjunct of a verb which s-selects an NP as its complement. When a CsP becomes the complement of a VP, it also shows a causative relation but both the agent of the causative action and the object which is caused to do the action refer to the same person.

The treatment of the suffix -kan as an inflection has an important advantage. With the analysis, the similarity of the pairs of sentences given above can be explained syntactically. The sentences in each pair have the same VP as the main lexical element, and their difference lies in the function of the CsP. Furthermore, the analysis also strengthens the theory that the production of a sentence is a series application of the complementation, adjunction, (attribution), and specification. A verbal sentence in Indonesia is equal to a VcP. A Vc may take a VP or CsP, a VP may take a NP, a CsP, or another category, and a CsP may take a VP or another category. The result of the processes is the d-structure of a sentence which, with the application of Affect-a, can be transformed into the s-structure.