A hearing at the Special Tribunal for Lebanon aimed to clarify laws the court will apply when trying those allegedly responsible for the truck bomb that killed Hariri and 22 others in Beirut on Feb. 14, 2005.
Tribunal President Antonio Cassese of Italy said the hearing showed that Lebanon "is set on a course for judicial accountability through the rule of law."
Prosecutors last month filed a sealed indictment to a judge who will take up to 10 weeks studying the charges and evidence before deciding whether the case can proceed.
By clarifying legal issues now, the court hopes to speed up the path to its first trial, expected to begin later this year with or without a suspect in custody.
It is widely expected that members of the Shiite militant group Hezbollah will be named in the tribunal's indictment. Hezbollah denies any involvement in Hariri's slaying and its leader, Sheik Hassan Nasrallah, has said his group would "cut off the hand" of anyone who tries to arrest any of its members.
Unlike other international courts, the Hariri tribunal can hold trials in absentia if suspects cannot be arrested.
Prosecutors and defense lawyers agreed Monday that Lebanese law, which the tribunal uses, already has a definition of terrorism while the international community has wrangled for years without coming up with a single definition for the crime.
"There is no reason to go further and create an overarching, worldwide, universal definition," prosecution lawyer Iain Morley said.
However he sought to refine the definition they will use at future trials, arguing that it was unnecessary to prove a political motive for a terrorist act.
"In any terrorist trial there will be an interest in why the event took place," Morley told the five-judge panel. "But if one fails to prove the exact reason ... that should not mean that the offense has not been properly proved."
In sometimes abstract arguments, lawyers and judges cited Greek philosopher Plato and 18th century French thinker Montesquieu, and discussed whether the 1914 assassination in Sarajevo of Archduke Franz Ferdinand could be classified as an act of terror.
Morley proposed his own definition of terrorism as an act by which "a substantial section of the public reasonably and significantly fears more than momentarily from the present onward indiscriminate personal harm."
Other topics under discussion were what constitutes a conspiracy, how to define intentional homicide and whether suspects should face more than one charge based on the same alleged crime - so-called cumulative or alternative charging.
Judges were expected to deliberate for weeks before issuing rulings.