Hallie's work generally explores the nature of ethics...good and evil, cruelty and kindness. His writing and statements have made particular reference to the admiration he holds for members of the French Resistance at Le Chambon-sur-Lignon.

• Scar of Montaigne
• The Paradox of Cruelty (1969)
• Lest Innocent Blood be Shed (1979)
• Tales of Good and Evil, Help and Harm (1997)
• In the Eye of the Hurricane: Tales of Good and Evil, Help and Harm (2001)
• From Cruelty to Goodness

In "From Cruelty and Goodness" he defines cruelty by what it depends upon to exist. He explains that all cruelty derives from a deficit in power. Examples are used such as Nazi concentration camps and slavery. "The power of the majority and the weakness of a minority were at the center of institutional cruelty of slavery and Nazi anti-Semitism." He also emphasizes that deep humiliation in institutionalized cruelty can be just as hurtful to the victim as episodic cruelty, cruelty where both the victim and the victimizer are aware of the harm being committed.He then goes on to purport that the redress of stopping cruelty isn't enough to negate or perfectly oppose cruelty. Hospitality is the only cure for cruelty. "It lies in unsentimental, efficial love." This is described as not only "being your brothers keeper" (protecting the weak), but also as staying true to the "negative injunctions against killing and betraying."