Explanation of the Loophole after Ab Aeterno by Lost Dogma

Readin all the discussions about "Ab Aeterno" I wanted to provide a theory about why the instructions are so important and need to be followed when trying to assassinate MIB or Jacob. I believe the loophole has to do with the assassin truly believing that either MIB/Jacob should be killed. He must be totally committed to the murder, without doubt. The dagger is irrelevant.

In "Sundown" Dogen gives Sayid the dagger warning him that this person is going to appear to him under the guise of someone you know and who died. He instructs Sayid to stab him in the chest before giving him any chance to talk. If he speaks it will be too late. The momentary doubt Sayid had when he saw Flocke was enough to keep Flocke from warding off the attack. Sayid also did not hate Flocke/Locke enough to truly want to kill him.

MIB tried to instill this unfaltering hatred in Richard during "Ab Aeterno" while he was still imprisoned on the Black Rock. By the time he was released Richard truly felt killing Jacob was the right thing to do to be reunited with Isabella. He may have been successful if Jacob had not subdued him.

On the other hand during the "Incident" Flocke had cultivated the hate in Ben for Jacob to such an extent that there was not any remorse or doubt when Ben had to decide whether or not to kill Jacob. It was not that Jacob spoke to Ben but his hate and murderous rage did not recede at all in the moments before he struck the blow. He truly hated Jacob and wanted him dead.