Board Thread:General Discussion/@comment-27079851-20171120082917/@comment-27295021-20171124080431

That's a valid excuse. When a human dies, their human souls goes on, and a demon take up residence in their body. So an ensouled Spike is as responsible for the actions of souless Spike as Buffy's postbox are responsible for sunny weather. The only reason it seem they are the same are because, as a consequence of inhabiting a human body, they retain most if not all memories of the "human" that once "owned" it. "What once were shape what we become", I believe Darla said.

So... Angelus and Angel are not the same person, they just look and sound alike and share memories, and the same can be said for ensouled and soulless Spike.