How we change what others think, feel, believe and do
Compartmentalization is a 'divide and conquer' process for separating thoughts that will conflict with one another. This may happen when they are different beliefs or even when there are conflicting values.
A person who is very religious and also a scientist holds the opposing beliefs in different cognitive compartments, such that when they are in church, they can have blind faith, whist when they are in the laboratory, they question everything.
There is sometimes honor amongst thieves, where together they act as honest people. Thieves also may be very honest in their family lives.
My son is an angel in school and a demon at home.
Compartmentalizing is building walls to prevent inner conflict. To some extent, we all compartmentalize our lives, living different value sets in the different groups to which we belong. Thus we may be ruthless at work but loving at home. We rationalize this by explaining that 'that's just the way it is'.
To help someone become more integrated as a person, one therapeutic technique is to take two chairs and have the person alternate between the two seats as they have a conversation with themselves, seeking to understand the other 'persona' and hence build passageways between them and become better friends with themselves (or at least gain greater acceptance and understanding). In time, the walls may crumble.
Where there are split personalities and there is a desire to extinguish one of them, then take the person to a higher level where they can see the common intent of both sides of the wall and how one side has mistakenly adopted the wrong path.
To get someone to do something that they would not normally do, help them build a new compartment in which to do it. Make as much different in this compartment as possible, including location, clothing, language, etc.