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Source: Dance Dance Dance
            Book VIII, 1155a.26 
Nicomachean Ethics
        
“Friends don't need the intervention of a third party. Friendship's a voluntary thing.”
Source: Dance Dance Dance
                                        
                                        Kenji Tanaka quoting a saying he heard from a (presumably fictitious) "very modern Zen master" in Ch. 13, p. 232 
The Ringmaster (1991)
                                    
Source: The Thrive Diet, Ch. 2
Source: The Meaning of God in Human Experience (1912), Ch. XII : The Will as a Maker of Truth, p. 140.
“Miracles are merely events that happen just when they are needed.”
“Don't condemn people who need it. Be very careful when that need becomes fanatical.”
                                        
                                        "Conversations in Port Townsend", interview with Tim O'Reilly, 1983. Reprinted in The Maker of Dune: Insights of a Master of Science Fiction (1987), edited by Tim O'Reilly 
General sources 
Context: What I'm saying in my books boils down to this: Mine religion for what is good and avoid what is deleterious. Don't condemn people who need it. Be very careful when that need becomes fanatical.
                                    
 
                            
                        
                        
                        