When does Just World Theory apply? Can someone explain how Just World Theory applies in real life? I have learned about it from textbooks but have trouble believing parts of it. Does it always apply? For example does it apply to individual situations like if you see someone get hit by a car you don’t normally think “that person must have deserved it” but is it more for an overall lifestyle for example if someone works a minimum wage job it would be “this person has a lazy personality”. I’m basically asking does Just World Theory have any qualifications for when it applies?

I guess psychology isn't like this, but does the Just World Theory apply to everyone in every situation all the time, or what?
The Just-World Theory/Belief/Hypotheses is an assumption that people eventually get what they deserves. Good people will eventually receive good things and bad people will eventually be punished, hence the world is "just/fair".


  One form of defensive attribution is to believe that bad things happen
  only to bad people or at least, only to people who make stupid
  mistakes or poor choices. Therefore, bad things won t happen to us
  because we won t be that stupid or careless. Melvin Lerner (1980,
  1998) has called this the belief in a just world the assumption that
  people get what they deserve and deserve what they get (Hafer, 2000;
  Hafer &amp; Begue, 2005; Lipkus, Dalbert, &amp; Siegler, 1996).


Fundamentally, this belief is motivated by our need to feel secure, to decrease anxiety from our vulnerabilities. After all, if bad things can happen to anyone, they can also happen to me regardless of what I do/don't do. Consequently, there are no guarantee that I'll receive "reward" for doing good.


  By using this attributional bias [belief in just world], the perceiver does not have to
  acknowledge that there is a certain randomness in life, that an
  accident or criminal may be waiting just around the corner for an
  innocent person like oneself. The belief in a just world keeps
  anxiety-provoking thoughts about one s own safety at bay.


You can imagine that this "randomness" can be overwhelming at times, especially when a tragedy strikes; for example when someone from work/school was raped.

Ironically, those who strongly believe in a just-world tend to unfairly judge that it must have happened because the victim did something wrong, e.g dressed inappropriately, flirting, etc. That way, the person can still believe that this world is fair, and if he/she doesn't do bad things, it will never happen to him/her.


  Research by Elaine Walster (1966) and others has focused on such
  attributions, which these investigators call blaming the victim (e.g.,
  Burger, 1981; Lerner &amp; Miller, 1978; Stormo, Lang, &amp; Stritzke, 1997).
  In several experiments, they have found that the victims of crimes or
  accidents are often seen as causing their fate. For example, not only
  do people tend to believe that rape victims are to blame for the rape
  (Abrams, Viki, Masser, &amp; Bohner, 2003; Bell, Kuriloff, &amp; Lottes,
  1994), but also battered wives are often seen as responsible for their
  abusive husbands behavior (Summers &amp; Feldman, 1984).
  
  ...
  
  When something bad happens to another
  person (as when someone is mugged or raped), we will undoubtedly feel
  sorry for the person but at the same time will feel relieved that this
  horrible thing didn t happen to us. We will also feel scared that such
  a thing might happen to us in the future. How can we cope with these
  fears and worries? We can protect ourselves from the fear we feel by
  convincing ourselves that the person must have done something to cause
  the tragedy. We feel safe, then, because we would have behaved more
  cautiously (Jones &amp; Aronson, 1973).


Does it always apply? No, not for everyone and not in every situation.

It explains one possible way people deal with anxiety of feeling insecure, but not as the only way. I couldn't find any scientific sources, but I imagine that people can see tragedy without feeling any insecurities, or can perceive the world as fair but have an entirely different reaction, or even doesn't see the world as just/fair in the first place.

References:

Elliot Aronson, Timothy D. Wilson, Robin M. Akert. (2010). Social Psychology Seventh Edition. New Jersey: Prentice Hall.