The opponents with whom Barclay deals most directly are all Calvinists. This is not simply because of Barclay's Scottish background and location, although that is significant. Calvinism was in Barclay's day the dominant theological movement in Britain. Nevertheless, it is the agreed premise of the universal depravity of the human heart that provides the common ground from which Barclay can build his alternative system. The most influential expression of Calvinism in Barclay's Britain was not Calvin's own writings, but the various documents produced by the Westminster Assembly of Divines, in particular the Westminster Confession of Faith and the Larger and Shorter Catechisms. The language, style and concerns of the Westminster Confession encapsulate a theological stance very familiar to Barclay, but also sum up exactly what he had felt bound to reject in his embrace of Quakerism. Barclay insists time and again that the Seed is nothing to do with any part of human nature.