In the previous sections I discussed the syntactic functions arguments may fulfil. In the following sections I will pay attention to the semantic functions or semantic roles of arguments. In this book the following roles will be identified:
Agent: the entity that controls a certain action or position. 
(42) egredere ex urbe, Catilina, libera rem publicam metu; in exsilium … proficiscere (`leave the city, Catilina, free the commonwealth from fear, go into exile', Cic. Catil. 1.20) 
(43) rem tene, verba sequentur (`concentrate on the content, the words will follow', Cato fr. 80.2 J.)
(44) Romani hostes in custodia habebant (`the Romans kept the enemies in prison')
Patient: the entity to which a certain action is applied or to which something happens.
(45) see rem publicam in (42)
(46) veteres leges aut ipsa sua vetustate consenuisse aut novis legibus esse sublatas (`the ancient statutes have either sunk into the decrepitude of their old age, or been repealed by modern legislation', Cic. de Orat. 1.247)Other semantic functions of arguments are the following:
Cause (for example: the wind opened the door)
Recipient (with dare)
Addressee (with dicere)
Direction (with se conferre)
Place (with versari, habitare) 
Following Dik (1978), still another semantic function (`Zero') may be recognized, for example Alexander in Alexander erat rex Macedonum. It
should be pointed out that contemporary linguistic theories offer different opinions both on the number and on the definitions of semantic functions. 
There is no one-to-one relationship between syntactic and semantic functions. The examples given above illustrate the fact that both arguments with the semantic function Agent and arguments with the semantic function Patient may fulfil the syntactic function Subject: not every Subject is an Agent nor is every Agent a Subject. The latter point may be illustrated with example (47): the Agent of pultando is identical with that of confregi:
(47) pultando … confregi fores (`I smashed the panels, pounding', Pl. Mos. 456)
With the action pultando an Agent is implied. However, no overt Agent is expressed. Therefore (47) has no constituent that can be labelled `Subject' of pultando.
Pinkster, Harm (1942-) , Latin Syntax and Semantics [info], xii, 320 p.: ill.; 24 cm. [word count] [Pinkster].