Krister Stendahl’s Three Rules of Religious Understanding are quoted here, there, and everywhere. They are never sourced, but no one seems to doubt that the rules are his. Stendahl is reported to have enunciated them at a 1985 press conference in Stockholm, Sweden – he was bishop of Stockholm at the time – in response to opposition to the building of a temple there by The Church of Jesus Christ of Latter-day Saints. His rules are as follows:
(1) When trying to understand another religion, you should ask the adherents of that religion and not its enemies.
(2) Don't compare your best to their worst.
(3) Leave room for “holy envy.”
By (3) Stendahl meant that you should be willing to recognize elements in another religious tradition or faith, elements you admire and wish might find greater scope in your own religious tradition or faith.
It is possible to put all three rules into practice, I submit, and still argue that not all religions are created equal, that a particular faith, from more than one point of view, is to be preferred above all others.
It is an additional sign of respect of a religion not one’s own to be clear about competing truth-claims that divide. Stendahl’s rules are a point of departure, not the end of a journey.
Krister Stendahl had a long career at Harvard Divinity School. Note this potpourri of an archive maintained by the HDS library; published and unpublished items thereof can be obtained via InterLibrary Loan. His scholarship was never dry or irrelevant to contemporary life. Two examples which deserve a wide reading:
“The Apostle Paul and the Introspective Conscience of the West,” Harvard Theological Review 56 (1963) 199-215. First published in Swedish, “Paulus och Samvetet,” Svensk Exegetisk Ǻrsbok 25 (1960) 62-77. Republished in Paul Among Jews and Gentiles and Other Essays (Philadelphia: Fortress Press, 1976) 78-96. Via Google books, much of the article can be read online. The full article is available through JSTOR. Ernst Käsemann heatedly replied to Stendahl’s proposal in “Rechtfertigung und Heilsgeschichte im Römerbrief,” Paulinische Perspektiven (Tübingen: Mohr, 1972 ) 108-139 = “Justification and Salvation History in the Epistle to the Romans,” in Perspectives on Paul (Margaret Kohl, tr.; Philadelphia: Fortress; London: SCM, 1971) 59-78. Stendahl replied to Käsemann in “Sources and Critiques” Paul Among Jews and Gentiles, 129-131. It deserves to be noted that the great exegete C[harles] K[ingsley] Barrett dismantled the pars destruens of Stendahl’s argument (but not the pars construens). See “Paul and the Introspective Conscience,” in The Bible, the Reformation, and the Church – Essays in Honour of James Atkinson (J. P. Stephens, ed.; JSNTSup 105; Sheffield: Sheffield Academic Press,1995) 36-48, reprinted in C. K. Barrett, On Paul (London: T & T Clark, 2003) 227-240.
Why I Love the Bible, Harvard Divinity Bulletin 35 (2007). The essay was adapted from an address delivered in 2001 as the Edward L. Mark Lecture at the Harvard-Epworth United Methodist Church –an annual event in the life of Harvard Divinity School United Methodists.