Productive morphological causatives in isiXhosa exhibit a case alternation with respect to the causee: it can be unmarked or instrumental. Much recent literature on similar alternations in causative constructions in other languages analyzes them as involving differences in the size or category of the constituent selected by the causative morpheme. We show that such an analysis cannot be extended to isiXhosa and that both alternants are verb‐selecting causatives. We propose instead that the alternation actually concerns the place in the structure in which the causee is introduced: in the specifier of the causative head itself in the unmarked‐causee construction, in a PP adjoined to the embedded verb phrase in the instrumental‐causee construction. This article thus adds to a growing body of evidence that the same thematic roles are not always assigned in the same syntactic positions.

中文翻译：

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生产伊西科萨语形态学成因的两个原因

伊西霍萨邦的生产性形态学成因在病因上表现出个案交替：它可以是未标记的或有工具的。关于其他因果结构类似变化的最新文献，最近很多文献都将其分析为涉及因果语素所选择的成分的大小或类别的差异。我们表明，这种分析不能扩展到isiXhosa，而且两个替代词都是动词选择的成因。相反，我们建议这种交替实际上涉及引入原因的结构中的位置：在未标记原因构造的原因性头本身的说明符中，在工具原因构造中与嵌入动词短语相邻的PP中。