star trek - Why four lights?

In Chain of Command, Part II Picard is tortured by Madred, a Cardasian who tries to force Picard to tell him there are 5 lights, when in fact the real number is four. He could have used any other method to break Picard’s will, but why four lights?

Is this a military training tactic, to instill obedience into troops? Or is it something else?

Answer

The torture scene in this episode is nearly verbatim from Nineteen Eighty-Four's "2 + 2 = 5". In the novel, the slogan is a primary example of doublethink, the ability of the totalitarian ruling party to exert such control they can even make people admit obvious falsehoods. Sensory evidence - or in the case of the novel, analytic truth - is internalized as insanity, and external statements are internalized as true, even when the subject isn't actually insane. The captors are showing their strength not just by forcing the captive, but by forcing reality itself.

At the end of the novel, the main character is being tortured into admitting that 2 + 2 is in fact 5. Unlike Picard, he does break - he admits to seeing five fingers even though he really only sees four. This begins a downward slide into compliance with the state.

Orwell invented this kind of situation as an allegory for the propaganda of the Nazi party, although he also applied it to Communism in Russia.

In the end the Party would announce that two and two made five, and you would have to believe it. It was inevitable that they should make that claim sooner or later: the logic of their position demanded it. Not merely the validity of experience, but the very existence of external reality, was tacitly denied by their philosophy. The heresy of heresies was common sense. And what was terrifying was not that they would kill you for thinking otherwise, but that they might be right. For, after all, how do we know that two and two make four? Or that the force of gravity works? Or that the past is unchangeable? If both the past and the external world exist only in the mind, and if the mind itself is controllable—what then?

Once that level of control is reached - when you can convince someone that your statements have primacy over their mental processes - you can make them do anything.