The Holy Lady Fatima Az-Zahra (as) has said:
Justice is a means for harmonizing the hearts.
This hadith used the word "harmony", a word that reflects the philosophy underlying justice. The goal of justice is to achieve the harmonization of hearts, which will end in achieving peace in the outside world.
From the words of Sayyidat Un-nissa' Fatima (as), we see that justice has two dimensions: external and internal. A justice that is to be established throughout the world must rely on a pre-existing justice within human hearts. Justice is not something that can be imposed through force. Rather, it is something that is established inside peoples themselves, creating peace and tranquility in the external world. The Qur'anic theory is thorough and comprehensive, being fundamentally a combination of the concepts of "justice" and "peace", in both internal and external forms. Those who cannot achieve tranquility in their own souls will not be able to bring peace in the rest of the world. The philosophy of "al-Jihad al-akbar" and "al-Jihad al-asghar" is based on this dialectic. If one wants to improve the outside world, he must first have made himself into a just person.
Adapted from the book: "The Awaited Saviour; Questions and Answers"