CT "Obi Wan taught you well..."

Yes. Force Smuggler and I both quoted the novelization's version of that scene.

 

D'oh, so you did. There must be some hex on that passage preventing people from noticing that it's already been posted.

 

Yea, I think you won this thread!

 

Just a thought........maybe Vader did have a hint of the force-ghost thing.

When he killed Ben, the vanishing body may have tipped Vader off that Ben meant what he said, "If you strike me down I shall become more powerful than you can possibly imagine."

It's unlikely Luke would have advanced in the force all by himself, and Vader was unaware of Yoda (as far as we know).

Perhap's Obi-Wan's dying line made an impact on Vader's subconscious. Afterall, when Anakin/Vader died he did become a force-ghost himself. Usually this is explained by "Well, he is the chosen one." But the movies do not give an explicit explanation.

Conclusion: Vader perhaps thought that Obi-Wan did train/influence Luke from beyond the grave.