Described by Pope Pius XII as the most important theologian since Thomas Aquinas, the Swiss pastor and theologian, Karl Barth, continues to be a major influence on students, scholars and preachers today. Barth's theology found its expression mainly through his closely reasoned fourteen-part magnum opus, Die Kirchliche Dogmatik. Having taken over 30 years to write, the Church Dogmatics is regarded as one of the most important theological works of all time, and represents the pinnacle of Barth's achievement as a theologian.