Do you think that there is a way that things are supposed to be? I don't mean a belief in the "best of all possible worlds" that Voltaire liked to make fun of, I mean a sort of basic sense that some things are just right and that sometimes a situation is just wrong?
Here is where the practical problem comes into play: it is only possible to be just if you have some idea of how thing ought to be. To be just is to say "this should be like that" and to then go about trying to make it so. Neither a determinist (who thinks that all things already are as they have to be), a modernist/non-supernaturalist (who has no grounds for claiming that there is any such thing as should be only what, in fact, is) nor a post-modernist (who doesn't think anyone has a right to talk about what should be for anyone else and besides how sure are they that there really is a this or a that anyway) can be just.
Now please don't misunderstand me, I am not saying that those folks can't be virtuous, kind, fair or egalitarian. They are often all of those things. In fact, they are often very just - I would point especially to the social gospel of the liberal Christian, modernist movement of the last century and the "social justice" movement so popular among contemporary post-moderns as wonderful and encouraging examples of people loving justice. What I am saying is that those worldviews give them no grounds for believing in or even really understanding justice. To the extent that they have it, they have it by tradition, by uncritical conscience or by divine Grace.
But it takes a pre-modern (eastern or western) to get justice.