His Reign Shall Have No End is a new introduction to traditional Catholic Social Teaching (CST). Too often, this subject is reduced to a grab-bag of catechetical truisms and welfare policies driven by modern secular, egalitarian, and pluralist assumptions. Instead, Dr. Kwasniewski traces all of its major elements back to the world-changing mystery of the Incarnation, whereby the Son of God became Head and Ruler of mankind in regard to goods both natural and supernatural. So far from being superseded by the "march of events" or what some would call "progress," the kingship of Jesus Christ-a revealed truth given consummate formulation by Pope Pius XI in his 1925 encyclical Quas Primas-is nothing less than the master key to CST's coherence and, more importantly, to the flourishing of nations no less than the beatitude of individuals. Wherever this kingship is ignored or denied, individuals, families, whole societies decompose like a body deprived of a soul; wherever it is welcomed in faith, Christian life revives and Christendom stirs from slumber. Divine Providence raised up Pope Leo XIII to guide the reconquest; his teaching is taken here as the unsurpassed guide to the thorniest political and economic questions that confront the human race at a time of tremendous upheaval.