Ergatively

an ergatively marked noun

In the light of this observation, it is interesting to note that the NP which is the Object of roll in (99) (a) seems to obey the same selection restrictions as the NP which is its Subject in (99) (b): cf. (100) (a) John rolled the ball/the rock/!the theory/!sincerity down the hill (100) (b) The ball/the rock/!the theory/!sincerity rolled down the hill Thus, the fact that the Object of roll when used transitively obeys the same selection restrictions as its Subject when used ergatively provides interesting independent confirmation of our initial assumption that the two NPs play the same thematic role, even though they have different constituent structure status.