The beattitudes are always intriguing. Sometimes they reassure. Sometimes they provoke. Sometimes they simply leave us realizing how short we fall. Yet, for most of them we can understand them. For the most part we know what a peace maker is or what a meek person looks like, even if we don't always exercise meekness or seek out peace. We understand persecution and poverty of spirit even as we usually try to avoid both.
However, hungering and thirsting for righteousness seems different. One part of really grasping this verse is knowing what hunger and thirst really are. Its probably a fair statement that most reading this have never really been hungry. Go a day without food or drink in America in you are on the ragged edge of deprivation. Yet, that is what Christ is calling us to experience regarding righteousness. To want it so badly that it seems like we are starving for it and will do anything to get it.
The bottom-line? The big idea? Righteousness is not what we do; its who we are. And we are not righteous in ourselves (Check out Romans 3!) However, if we are poor in spirit and mourn over that state, the Holy Spirit will begin to build in us a true hunger and a real thirst for righteousness. Christ's righteousness!