An Ideal Storm
Justice, as it pertains to equality and treatment of others, is an important factor in relationships. Shakespeare used it in many of his plays to illustrate particular character's flaws and virtues. Meaning varies from character to character but on the whole he showed it as the ultimate stabilizer, that a character with justice in his heart was always good and had balance in his life. It is also arguable that he believed to be good you must be just. He certainly did not believe that justice was a common occurrence. Among all his characters only a few could be called truly just, this might have something to do with the fact that love and jealousy tend to interfere with all virtue not just justice and there was lots of love and even more jealousy in his works. It is possible that he used it as an absolute example of virtue because he believed that all others stemmed from it, it is also possible that he simply had to choose one and it was rather random.
"The Tempest" is a very good example of his use of this particular characteristic because of the wealth of interactions that used it, the first among these is Prospero and his slave Caliban. Many of the ways he treated Caliban were justified in that Caliban had attempted to violate his daughter after they had taken him in and tried to teach him and help him to overcome his past. Unjust however was how he did not give him a chance to redeem himself or try to change his ways when he had the means and opportunity. Shakespeare's reasoning in doing this was possibly to make the characters seem more real and not as caricatures in a parable. The purpose was to show Prospero as a rather crusty old man and Caliban as irredeemable. Although if Caliban was irredeemable than Prospero's treatment of him was not unjust. There is a Shakespearean thought process for you.
Another example of that process is Prospero and the sprite Ariel. Prospero turned Ariel into his slave after freeing him from a tree where he had been imprisoned and tortured by the witch Sycorax. The magician viewed it as an obligation of Ariel to serve him after being freed by him. However the impression is given that Ariel had been serving him for some time when the events of the Tempest first begin, Ariel himself protests his servitude and Prospero threatens to return him to the same torture if he continues to complain about his slavery. This interaction is harder to dissect than the previous one in that there seems to be no purpose to it besides the fact that if Ariel had been freed many of the events of the book could not have taken place, therefore it was possibly only a plot device. On the other hand Prospero seems quite fond of Ariel especially later as the sprite fulfils his requests with increasing dexterity and abandon. As an offset to Prospero's antagonistic relationship to Caliban his relationship with Ariel seems to be there to illustrate the friendship that can grow between a man and his servant or slave.
Last but not least in examples is Prospero's treatment of Prince Ferdinand which is much easier to define as he exacted it from the position of a father not a master. As a father he was completely within his rights to treat the Prince like he did to judge his worthiness after seeing such corruption from his father the King. Even that though did not perhaps excuse the slavery he forced upon him to win his daughter. It may have been temporary but was extreme and unnecessary, though that seems to be a common occurrence with Prospero's personality. The reasoning behind his actions this time was obviously to protect Miranda so they would not have a repeat of the incident with Caliban. To make it more logical still, he realized that the attraction was mutual and Ferdinand would not have to do much or anything for that matter to win Miranda's trust and bed. Shakespeare in this example wished to display Prospero's undying and incredibly deep devotion to the only family he had left that despite his many faults all he truly wanted was to make sure that Miranda would have the life and love he never had.
Finally, it seems that Shakespeare made this play as a treatise on human relations and meant to show that the bonds of family should be held dearer than is common for them to be. He showed that Prospero's treatment of Caliban is just for a master when the slave is irredeemable that it is not acceptable when the servant is good and loyal as Ariel and most importantly that there are no lengths that should not be gone to when the safety and happiness of a family member- of a child- is at stake, even if it is unjust or painful. Shakespeare meant this to be taken as a story of moral and meaning. Perhaps because of his own family life or the lives he saw around him he held those relations the most dear and most important in a man's life, so important in fact that all former quarrels between individuals should be disregarded if only to make family and children happy.
In lieu of being described as a romantic which though quite ironic is not precisely true, Shakespeare must be regarded as more of an idealist than anything for he realized what was truly important in a persons life and he strove to make it apparent that such things are far more significant and worth fighting for than quarrels and feuds that are petty in comparison.