All you have to do to arrive at that conclusion is take a look at how Webster's defines it — “the maintenance or administration of what is just, especially by the impartial adjustment of conflicting claims or the assignment of merited rewards or punishments.” 

Now let's break up that definition into its constituent parts. 

First, defining the word “justice” by saying that “justice” is “what is just” is like defining the word “rain” by saying that “rain” is rain. It's a useless exercise. 

Then we have the words “impartial adjustment of conflicting claims.” Given that it's not possible for anyone to be objective, disinterested, and so on, there can be no such thing as an “impartial adjustment of conflicting claims.” 

And finally, we have the phrase “assignment of merited rewards or punishments.” The key word, here, of course, is the word “merited.” What I think someone merits could easily be 180 degrees away from what you think that that person merits. And we'd both be right. And we'd both be wrong. 

So what then is “justice”? The answer is, “I don't know.” 

You know, someone was once asked to define the word “God.” He replied, “I know what God is. But as soon as I try to explain Him, I don't know anymore.” 

Maybe the word “justice” is like that. I know what “justice” is. But when I try to define it, I don't know anymore. 

You know, it strikes me that there's something analogous between what underlies the word “God” and what is meant by the word “justice.” And maybe that's because God is the only one who knows what justice really is. 

Think about it.