If you're going to just make stuff up, dude, at least do it in Voice.

Dementor said, "Yes, dragonborn can absorb the souls of other dragonborn. This how Martin Septim absorbed the souls of his ancestors when he shattered the Amulet of Kings."

Now -that's- interesting. There has been some suggestion that Amulet of Kings absorbed the souls of past Emperors before (can't remember where) and thus Martin absorbed them all before...dying? Attaining godhood? Transcendance into Aetherius? Here's a completely insane idea...is the Dragonborn of Skyrim the amalgamated souls of Martin re-incarnated as a singular personality? In other words - is the Dragonborn the Amulet of Kings incarnate? Ooooh...

Geez, I hope not. That would mean the Dovahkiin has a bit of the soul of Pelagius the Mad floating around in him.

Well, it would explain how he ended up in the mind of Pelagius during Sheogorath's quest in Skyrim. It's pretty easy to go into the mind of a dead person when their soul is a piece of yours.

As circumstantial evidence, this cannot be used in support of Scourgicus's theory directly.

This is an assertion. We do not fully understand what kind of a connection exists between the soul and the mind of a person. Therefore, while your statement is plausible, it is also essentially baseless.

Both good points. Though we also know it's possible to consult the Amulet of Kings, and that the oversoul of Emperors can be consulted down to individuals, to the point that Hestra and Shor-El had different commentary about what happened when the dragon broke. We also know from numerous quests that ghosts can at least present a simulacrum of the dead person they are born from, doing everything from attempting to pursue last calls for vengeance (lysandus) or attempting to re-establish long forgotten (well, not forgotten, but whatever) rule (Potema), to making trueflame burn with a brilliant fire. Souls can clearly present something resembling a mind, and the presence of Pelagius' soul (either as a plaything of Sheogorath or some other thing) would go a long way to explaining why walking down a corridor let's you visit a dead guy's mind.

Rather than dismiss this without offering my own thoughts, I'm going to go ahead and say "it's entirely possible, and here's why:"

We have a precedent (potentially) in the elder scrolls lore for the fusion/melding of souls into a single, (potentially) cohesive whole - The Dwemer. Someone get (what's left of) Velorien in here.

Dovahkiin is even established as anologous to Numidium via Arniel's endeavor.

Sorry to resurrect a conversation that appears to have died off...but I need Muertos1130 to explain that last statement. You've got something interesting there, I think.

After Arniel goes 'poof,' the Dovahkiin gains the ability to summon his shade for no discernable reason at all. It is inferred that, because the Dovahkiin has the soul of a dragon, and is therefore divine in some respect, Arniel succeeded in repeating the Dwemer experiment on a much smaller scale, by subsuming himself into the Dovahkiin. The dwemer became the divine skin for Walk-Brass, which supposedly would have otherwise been a (new?) god; the Dovahkiin is (potentially) the incarnate splinter (however small) of a god, and as such he served as a sufficient divine-spark for the purposes of the experiment. The tragic/hilarious thing about all of it is that Arniel had no idea what the hell he was doing; he engaged in child-like mimicry of some of the most complicated magic/manipulation of reality ever undertaken by mortals, and paid the price for his audacity.

Keening as tuning fork! Brilliant! XD