What's the relationship between the Gospel of Christ and Social justice?

This quote came into my inbox this morning.  I thought it was so clear and simple - so, I decided to post it here!  What encouraged me is that it comes from the international director of John Stott Ministries...  I have some reading to do!

It is not a matter of engaging in both the gospel and social action, as if Christian social action was something separate from the gospel itself. The gospel has to be demonstrated in word and deed. Biblically, the gospel includes the totality of all that is good news from God for all that is bad news in human life?in every sphere. So like Jesus, authentic Christian mission has included good news for the poor, compassion for the sick and suffering justice for the oppressed, liberation for the enslaved. The gospel of the Servant of God in the power of the Spirit of God addresses every area of human need and every area that has been broken and twisted by sin and evil. And the heart of the gospel, in all of these areas, is the cross of Christ. 

- Christopher J. H. Wright
International director of John Stott Ministries (from Knowing the Holy Spirit Throught the Old Testament)