Herrick's research interests included rhetoric and argumentation, new religious movements, technology and spirituality, and the discourse of futurism.
[1] His early books are guides to the discipline of scholarly argumentation that discuss both traditional rhetorical techniques and contemporary applications for students and academics.
[6] Herrick's research interests included the relationship between Christianity and rhetoric, and the intersection of spirituality and public discourse.
Herrick wanted everyone to recognize "the pervasiveness of persuasiveness" and defined rhetoric as "the systematic study and intentional practice of effective symbolic expression".
Of Herrick's 1997 book, The Radical Rhetoric of the English Deists, Lester C. Olson of the University of Pittsburgh wrote, “It is...an important contribution to eighteenth-century studies and scholarship on the history of Britain.”[11] James W. Sire called 2003's The Making of the New Spirituality “[a] lucid intellectual history with important implications for navigating the religious currents of our day.”[12]