Family...Why couldn't they see William?

[Kemy]

Something in the episode, and another thread here, has me wondering.

Tara's spell hid any demon from the sight of the Scoobies, but they didn't go into specifics of what amount of demonic essence was invisible.

The Layoff (spelling?) demons are as about pure blood as you can get on Earth since most are half breeds of a kind (according to Anya in season 3) and were completely invisible.

Tara said she wanted to use the spell to "Hide her demon side", implying the spell only hid the demon essence, not its host, they would still have been able to see Tara, just not her demon side.

So why could Buffy not see William?, even if the Vampire essence of Spike was hidden as per the spell, had Tara been part demon and expected them all still to see her Human half, then technically shouldn't the William part of Spike been visible?

Or is the Vampire essence so deeply infused into the body as to hide the Human in the host altogether?

[Lyri]

because 'William' didn't exist. Spike didn't have a soul, he was the 'soul' of a demon inhabiting the corpse of a human. there was no trace of William left inside Spike at the time of Tara's spell, he was a demon.

[Kemy]

Yes but the physical body is still that of William/Spike, another creature is now in residence inside but since Demons are souless by nature, and Tara fully expected them to still see her Human body as it was, then no matter what was "at the controls" it would still look like the original person. Spikes body should still have been visible since it was still the Human part.

[benboy606]

Yes, but William is gone. That is his body, but not him. It's his soul, and that's what makes a demon a demon. They have no soul.

Tara, imo, literally meant to hide herself.

[Kemy]

Tara meant only to hide the Demon "part" of her and remain with them. If it were as simply as not wanting them to see her at all she would have run away or even gone back with her parents.

Beth: They will. Unless you ... do some kind of spell on them .... (sees Tara's face) You did!
Tara: N-no!
Beth: You did something to them. I'm telling your father.

She starts to turn away. Tara grabs her arm.

Tara: No! No, it wasn't anything!
Beth: You think you can just go around cursing people? Your dad's gonna pop.
Tara: It was just so they wouldn't see. So-so-so they wouldn't see the demon part of me. (teary) Please don't tell Dad. It's harmless.

Demons are Souless too, so she would have been had her fathers story been true, yet she still expected them to see the "Tara" part of her like always.