The irony of slavery
Throughout the book, attention is paid to slavery from many points of view, and every time, slavery is shown to be a foolish, evil practice. The irony of slavery in the stories is that the slaves are not treated as people, but white people are the ones who act cruelly and inhumanely. If anyone is being savage, it's Faulkner's depiction of white men.
The irony of death
No matter how complicated the story seems, they all have the same end. Faulkner includes human death as a central issue throughout this collection, but there is one extremely ironic occurrence of death: Isaac's first successful hunting trip. In "The Old People," (the title will be relevant), Isaac kills a deer. It is the first time he has killed an animal of any kind, and he killed a respectably-sized buck. Instead of death representing finality, though, it represents something else. Isaac is anointed with blood, a symbol for death, and then he sees a strange spirit, a strong elder buck that comes to Isaac in a religious vision. In this instance, death brings religious ecstasy and spiritual enlightenment.
The irony of the ending
Without explaining much else, Faulkner ends the book with a vignette of a grandmother picking up the dead body or her grandson who was executed by the state for crimes. This image concludes the collection, which is a bit of a weird note to end on, but also notice that the image itself is ironic. Typically, who dies first, the grandmother, or the grandson? The irony is signaling in yet another way that death is perplexing.
The irony of Lucas Beauchamp
Lucas is ironic because his dilemma about not being "white enough" drives him crazy. He is constantly worried about being a slave, which only makes him more racist (even against himself, ironically). Instead of using that dilemma as a reminder that slavery is completely unfounded and evil, Lucas goes the other direction and spends his life trying to find something: a buried treasure. But that treasure represents what Lucas really wants: to approve of himself. He cannot hate himself for racist reasons and still love himself.
The irony of honor and inheritance
Honor and inheritance are simultaneous rewards from one's ancestors. In tribal communities all across the earth, the standard view was that if one lived honorably, they would receive the approval of their ancestors, through blessings in their life, through a glorious sense of identity, and through inheritance. But not in this book. The central irony of the book is that Isaac McCaslin rejects his birthright completely. He doesn't want his ancestor's blessing, because their sense of "right and wrong" is incorrect and dishonorable. Isaac doesn't want the blessing of bigoted, hateful racists who mistreat nature and mankind alike. That's why Isaac receives honor from his true family—nature itself.
