Ebert wrote:

The central character in "Antichrist" is not supernatural, but an ordinary man, who loses our common moral values. He lacks all good and embodies evil, but that reflects his nature and not his theological identity.

This man, known only as He, is played by Willem Dafoe as a somber, driven, tortured soul. The film opens with He and his wife, She (Charlotte Gainsbourg), making passionate love. This is a moment of complete good. In the next room, their infant son begins to crawl around to explore and falls to his death. This in itself is a neutral act. It inspires the rest of the film, which labels itself in three stages: Grief, Pain and Despair.

We must begin by assuming that He and She are already at psychological tipping points. She has been doing research on witchcraft, and it leads her to wonder if women are inherently evil. That may cause her to devalue herself. He is a controlling, dominant personality, who I believe is moved by the traumatic death to punish the woman who delivered his child into the world.