"Hand to ball or ball to hand?" Nothing stirs the passion like a controversial handball decision.
You've only got to look at players and managers jumping up and down enraged at a dodgy penalty to know that.
A ball slams into a player's arm and one team is screaming for a penalty, while the others are claiming it was an accident.
It's a tricky one for the referee to call in the heat of the moment.
So what is 'deliberate' handball?
In Fifa's Laws of the Game 2005, Law 12 says a free-kick or penalty will be awarded if a player "handles the ball deliberately (except for the goalkeeper within his own penalty area)".
Page 67 of the document gives "additional information for referees, assistant referees and fourth officials".
It adds: "Referees are reminded that deliberately handling the ball is normally punished only by a direct free-kick or penalty kick if the offence occurred inside the penalty area.
"A caution or dismissal is not normally required."
However, the document fails to describe what constitutes deliberate handball, which places the responsibility firmly on the referee and referees' assistants.
Former Premier League referee David Elleray said the referee's interpretation depends on whether the hand or arm is in an "unnatural" position at the point of contact.
"Referees look at two specifics - did the hand or arm go towards the ball or in a manner which would block the ball, or is the hand in a position where it would not normally be?" Elleray told BBC Sport.
Referees often consult their assistants on decisions
"The challenging decisions are if the defending player spreads their arms to make themselves bigger.
"If the ball hits the arm then the referee must decide whether this action was to deliberately block the ball or whether the player has raised their arms to protect themselves - especially if the ball is hit at speed."
The referee and referees' assistants, therefore, have a matter of seconds to weigh up these factors, and take the appropriate action.
And there will always be at least one manager, 11 players and thousands of fans who will insist they have been hard done by.