Because the author contends that "the welfare of the church and her members is deeply concerned in the preservation of the purity of God's worship," he here defends the old paths of Protestant worship in opposition to the will-worship of Popery, Socinianism and Arminianism.

Herein he shows how the singing of songs other than the Psalms (in public worship) violates the second commandment, dishonors God and brings His wrath upon individuals, churches and nations.

Anderson also answers a number of objections against exclusive Psalmody which are still common today; for example the objection, "with respect to the nature of singing, as if there were no difference between it and prayer, except in the manner of performance." This is a valuable contribution to the defense of exclusive Psalmody.