The development of the Tocharian causative system - top-down or bottom-up?

Tocharian possesses a highly complex verbal system and has played a major role in theories about the PIE verb in recent decades. While it is certainly true that Tocharian deserves the highest attention for theories about the protolanguage, not every trait of its verbal system has to be explained by direct top-down developments and not every trait can be directly transferred onto the proto-language. The paper discusses the Tocharian causative stems and argues that an inner-Tocharian development for the system of causatives is more likely than deriving the various stems from respective PIE stems directly.