Having briefly considered the contribution by the English Puritans and the 17th century Confessions of faith, the next wave of theology was a Reaction to Protestant Orthodoxy (Seventeenth and Eighteenth Centuries). This era (18th Century) introduced Rationalism and Pietism.
Rationalism emphasized the supremacy of human reason, with no need for revelation. Deism, a form of Rationalism, teaches that God is impersonal and that all can be discovered through natural means without Scriptures. This is an intellectual appeal to the human mind. It is opposed to the Bible.
Pietism emphasized personal religious experience. Pietists continued to believe in Scripture and the importance of revelation. Their emphasis on experience, however, tended to place experience ahead of Scripture. This movement emphasized small groups apart from the larger church. Pietism shunned doctrinal differences as less important. Pietism sought to equip ministers apart from theological training, relying more heavily (if not exclusively) on Christian experience. Pietistic ministers had to be good communicators, with messages relevant to the hearers, even if not terribly meaty in content (does this sound familiar in our day?). Pietism emphasized regeneration, but in a new way, through personal experiences like Finneyistic altar calls.[1] Pietists emphasized the changed life and what salvation could do for people—experientially. Pietism can be seen in some of the Puritans and then in Wesleyanism. It evolved into rank experientialism and individualism—which is rampant in our day.
These two pursuits, while different, arrive at a common destination. The great Benjamin Warfield wrote of these two: “Pietist and Rationalist have ever hunted in couples and dragged down their quarry together. They may differ as to why they deem theology mere lumber, and would not have a prospective minister waste his time in acquiring it. The one loves God so much, the other loves Him so little, that he does not care to know Him.” (Warfield, “Our Seminary Curriculum,” Selected Shorter Writings, I, 371)
Note:
[1] Charles Finney (1792-1875) introduced “decisionism,” based emotional appeals to people to “accept Christ” by responding to “altar calls.” These measures, though considered standard procedure to many modern evangelicals, were unheard of until this time.