His high appreciation of Christianity, which contrasts with the contemptuous estimate of the contemporary rationalists, rested on a firm belief in its essential humanity, to which fact, and not to conscious deception, he attributes its success.
Hengstenberg, he endeavoured to convince the rationalists that it was their duty voluntarily and at once to withdraw from the national church.
Hugh James Rose had published in England (1825) a volume of sermons on the rationalist movement (The State of the Protestant Religion in Germany), in which he classed Bretschneider with the rationalists; and Bretschneider contended that he himself was not a rationalist in the ordinary sense of the term, but a "rational supernaturalist."
By this lexicon Teller had put himself amongst the most advanced rationalists, and his opponents charged him with the design of overthrowing positive Christianity altogether.
Nor was it till late in the 18th century that criticism seriously challenged the dominance of the Protestant scholastic treatment of the Old Testament on the one hand, and the rough and ready, uncritical explanations or depreciations of the Rationalists on the other.