In Plato's Republic, Thrasymachus provides a definition of justice that Socrates rejects, for it does not get to the heart of justice but is actually more about power. Let's look at this in more detail.

When Thrasymachus says that "justice is the advantage of the stronger," he means that those who have more power get to decide what is right and enforce their decision for everyone else. In other words, in Thrasymachus's mind, "might makes right." Those who are powerful get to make the laws, and then everyone else is supposed to obey them.

Socrates then challenges Thrasymachus with the observation that rulers can make bad laws, but Thrasymachus disagrees. Rulers do not make mistakes, he maintains. Socrates then shows that rulers actually can make mistakes, especially about justice, when they focus on their own desires and interests rather than those of their subjects.

For Thrasymachus, then, justice is determined by whoever happens to be in charge. Now think about examples of this in today's world. You might consider a situation in which someone in authority in a workplace makes a decision that works to their own benefit without considering the effect it would have on coworkers.