reflects the Word of God and the struggle of conscience of those who came to believe it did not fully do so (e.g. William Robertson Smith). Some Presbyterian Churches, such as the Free Church of Scotland, have no such "conscience clause". The Presbyterian Church (U.S.A.) has adopted the Book of Confessions, which reflects the inclusion of other Reformed confessions in addition to the Westminster Standards. These other documents include ancient creedal statements (the Nicene Creed, the Apostles' Creed), 16th-century Reformed confessions (the Scots Confession, the Heidelberg Catechism, the Second Helvetic Confession), and 20th century documents (The Theological Declaration of Barmen, Confession of 1967 and A Brief Statement of Faith). The Presbyterian Church in Canada developed the confessional document Living Faith (1984) and retains it as a subordinate standard of the denomination. It is confessional in format, yet like the Westminster Confession, draws attention back to original Bible text. Presbyterians in Ireland who rejected Calvinism and the Westminster Confessions formed the Non-subscribing Presbyterian Church of Ireland. John Gresham Machen, the prominent Presbyterian theologian and Professor of New Testament at Princeton Seminary between 1906 and 1929, led a revolt against modernist doctrine in his Christianity and Liberalism (1923) that critiqued theological modernism. He argued that modernism and liberal theology was a false religion, a pretender that cloaks itself in Christian language – "Liberalism". This religion is a marriage of naturalism, humanism, secularism, and sentimentalism all rolled into one. Worship and sacraments Worship Presbyterian denominations that trace their heritage to the British Isles usually organise their church services inspired by the principles in the Directory of Public Worship, developed by the Westminster Assembly in the 1640s. This directory documented Reformed worship practices and theology adopted and developed over the preceding century by British Puritans, initially guided by John Calvin and John Knox. It was enacted as law by the Scottish Parliament, and became one of the foundational documents of Presbyterian church legislation elsewhere. Historically, the driving principle in the development of the standards of Presbyterian worship is the Regulative principle of worship, which specifies that (in worship), what is not commanded is forbidden. Over subsequent centuries, many Presbyterian churches modified these prescriptions by introducing hymnody, instrumental accompaniment, and ceremonial vestments into worship. However, there is not one fixed "Presbyterian" worship style. Although there are set services for the Lord's Day in keeping with first-day Sabbatarianism, one can find a service to be evangelical