Even though The Pledge (2001) is murder-mystery
film, it is fundamentally a tragedy without regard to the murder. Jack Nicholson
plays Jerry Black, a retired police investigator who loses everything because
he is faithful to a pledge that he made to the parents of the young girl who
had been raped and murdered by a serial killer. It is Jerry’s fidelity to the
pledge that is highlighted throughout the film, and ultimately ends in his
ruin. The film thus depicts what in Kant’s ethic is the ability of rational
beings to be taken as promise-keepers bound by the promises we make as if they
had the necessity of law.
The full essay is at "The Pledge."