Sentence:  In numerous works over the past two decades, beginning with the pioneering work of Gruber (1965), Fillmore (1968a), and Jackendoff (1972), it has been argued that each <WSD>Argument</WSD> (i.e. Subject or Complement) of a Predicate bears a particular "thematic role" (alias "theta-role", or "&theta;-role" to its Predicate), and that the set of "thematic functions" which <WSD>Arguments</WSD> can fulfil are drawn from a highly restricted, finite, universal set. 
Meaning of the word marked with <WSD> tags:  (linguistics)  Any of the phrases that bears a syntactic connection to the verb of a clause.