Did Cain truly kill his brother because his sacrifice was not accepted and Abel's sacrifice was accepted?
Certainly, this event was the catalyst that led Cain to kill but if we stop there we run the risk of not understanding Cain's motives and when we do not understand someone's motives, we can easily conclude that whatever caused him to act as he did does not concern us; we will not do as he did.
While murder is -- thank God -- far away from our daily lives other mortal sins can be closer: gluttony and lust are all too common and so is the root of all evil: pride. While they may not compare to murder, nevertheless they can land us in Hell if we die unrepentant. Therefore, whenever we encounter a sin we do not understand it is time to roll up our sleeves and study deeper and longer in order to receive the graces that God has reserved for us in Scripture.
Here we take a critical detour via the theory of mimesis that Rene Girard has developed and which helps us to unlock this difficult chapter and provide a rich and insightful explanation to seemingly strange utterance by God such as when he puts a mark on Cain's forehead after exiling him so that he may be protected. Why does God protect Cain when he clearly deserves to die for killing his brother? What is the purpose of this mark and why does God declare that anyone who kills Cain will face a sevenfold vengeance?
Rene Girard expounded his theory in a series of books culminating in his most important work things hidden since the foundation of time. This lecture provides an overview of his theory, explains why it is important, and shows how illuminating it can be when applied to Scripture. Using it we get to discern Cain's motive and understand what led him to kill his brother.