As humans, we crave explanations for the evil we encounter so we can try to make sense of it. We never got that for Charles Manson.

Despite all the books and movies about him, all the songs and artwork and TV specials and essays and merchandise and internet fan sites, Manson remained as unknowable and inscrutable as he was in August 1969, when the “family” he assembled in Southern California went on a murderous rampage that took seven lives.

There have been many bizarre murders since then, but none has gripped us like the one orchestrated by Manson. The violence seemed random. The lurid details — drugs, group sex, ritual killings, words scrawled in blood — were irresistible. The banal elements were scarily commonplace — the single mother whose life of petty crime left Manson in foster homes and reformatories, the Dale Carnegie book that taught him how to influence people, the Beatles lyrics that inspired him, his failed attempts to become a rock musician. And the women who were his followers were familiar — middle-class misfits and loners from broken homes whom Manson knew how to seduce, abuse and control, and to persuade to murder again and again.

He was evidence that unspeakable evil can find anyone, and he inhabited our psyches as a real-world Satan. The cult of Manson was as much about our response to him as it was about Manson himself. And he haunted us for decades, creeping out from our subconscious every time he came up for parole. That won’t end with his death Sunday.

Manson ultimately will be remembered for more than the awful violence of that hot August night. His most prominent victim, actress Sharon Tate, who was married to film director Roman Polanski, was eight-and-a-half months pregnant when she was slaughtered. Her mother became a powerful spokeswoman for victims’ rights and was instrumental in the passage of a law that allowed for victim impact statements in California, a right that has spread in some form to all 50 states.

But Manson’s legacy mostly will be as a metaphor for evil incarnate and the uneasiness he instilled in us. Manson once said, “I am just a mirror. Anything you see in me is you.”

It wasn’t true, but the possibility was terrifying.