Frawley has proposed three argument roles which are grouped under the category of logical actors: the roles of agent, author and instrument. Based on his descriptions
of the category of logical actors, and the roles themselves, I propose to make two points in this paper. First, I will show that based on syntactic evidence there exists a fourth role in this category, which I will name causer. Secondly, in my opinion there is not a clear theoretical discussion of the relationship between the roles in the category of logical actors. I will propose that, through use of a binary feature system, we can show more clearly the relationship the roles have to each other with respect to their semantic and syntactic function.
Armstrong, S. (1995). Thematic roles: a semantic feature analysis. Calgary Working Papers in Linguistics, 17(Winter), 51-56.