Lyric discussion by TheTpMovement 

I will map out the song as clearly as I can and hopefully it makes sense. :-)

Interpretation A

The song is sung from the point of view of a man, the Last Firstborn. Why is he called the 'Last Firstborn'? Because his father died fighting in war, and hence only had the one son: him. His father died for his freedom, but his father also committed sin: murder. And there we have the religious theme coming into play, which begs the big question that torments the speaker:

"How can I reconcile the fact that my father -- a good man, my role model, my light -- fought and died for my freedom, for my life, but did so by committing murder?"... "Would he then go to hell?"... "And as I am fighting now, following my father's legacy, murdering other Last Firstborns who are also following their legacies, will I be allowed into heaven? Or will I be left alone?" "Do I commit to my father's cause so that he did not die in vain? I was, after all, his Last Firstborn, his only hope, his only continuation... Or do I leave it all behind? But if I do that, then why did my father die?!?! For what??"

OR

Interpretation B

It could be that his dad is actually a criminal who committed murder and is being taken away to jail for a life sentence, and the son struggles -- he cannot fathom the image of his father committing such a crime -- but he does sort of imagine it, and also think of himself in that position because he is his dad's legacy, his Last Firstborn, and he is now emotionally and psychologically scarred. And this state is threatening his morality and is potentially dooming him to mimic his father's actions.

I mean, keeping both possibilities in mind... Comments are after each line in (****)

Beginning

(1) Oh man, I can't believe that you did what they said you did (I can't believe you killed people in a war, dad) And to this day I've still gotta say that in my mind I question it I wish I knew what you had meant before you went and left me wondering to just an echo of your voice 'Listen...' ( before his dad left to go to war, he kneeled down and said: "Listen...)

(2) Oh man, I can't believe that you did what they said you did (I can't believe you committed murdered, dad) And to this day I've still gotta say that in my mind I question it I wish I knew what you had meant before you went and left me wondering to just an echo of your voice 'Listen...' ( before his dad left to go to jail, he kneeled down and said: "Listen...)

Now read through all of the lyrics two times, first keeping Interpretation A in mind, and then Interpretation B. :o)

Oh, and I forgot to mention something important. Where he says "mortal shell" the shell in this case has NOTHING to do with a shell from war/from a weapons.

The shell, in this instance, 100%, is referring to the human body. The human body is a mortal shell.

Think about that.

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