Reinhold Niebuhr on moral motivation 

Preachers who are in danger of degenerating into common scolds might learn a great deal from H’s preaching style. I am not thinking now of the wealth of scholarship which enriches his utterances but of his technique in uniting religious emotion with aspiration rather than with duty. If he wants to convict Detroit of her sins he preaches a sermon on “the City of God,” and lets all the limitations of this get-rich-quick metropolis emerge by implication. If he wants to flay the denominationalism of the churches he speaks on some topic which gives him the chance to delineate the ideal and inclusive church.

On the whole, people do not achieve great moral heights out of a sense of duty. You may be able to compel them to maintain certain minimum standards by stressing duty, but the highest moral and spiritual achievements depend not upon a push but upon a pull. People must be charmed into righteousness. The language of aspiration rather than that of criticism and command is the proper pulpit language.

from Leaves from the Notebook of a Tamed Cynic (1929), 92.