By the power of truth, I, while living, have conquered the universe.
Posted by: Cmdr DaeFaron
Possibly... if he hadn't been standing in a halo's control room when the array fired.
The only evidence we actually have for that is Legends, and that was just Cortana's interpretation so it's not reliable evidence.
There are hints that he was at 04, but the evidence against that has led Vocieferous seems to believe that Didact fired the Rings from the Ark.
To reiterate what I said last time.
From the Terminals:
How formal of you, Librarian. We're receiving shipments of indexed beings more frequently than communications. Don't compound scarcity with brevity.
This line clearly shows that the Didact is at the Ark, the Librarian is shipping indexed/catalogued beings to him - which were all stored at the Ark.
Later, the Librarian says:
Something is wrong! It's moving away! At night I can see it - flitting shadows - black against the stars. Thousands of ships! Not spiraling outward but heading for the line. This is the tipping, Didact. It's no longer feeding.
It's coming for you.
To which he later replies:
Mendicant Bias is trying to prevent us from firing the Array. He speeds back to the Ark, but he won't succeed. Offensive Bias will stop him, and I will burn this stinking menace in your name.
And then? I will begin our Great Journey without you, carrying this bitter record. Those who come after will know what we bought with this [false transcendence]-what you bought, and the price you paid.
Now why would Mendicant Bias go to the Ark if the Didact was at a Halo? that wouldn't make sense, he could just send the Flood to whatever Installation the Didact was on with his 5/6 million ships and destroy it, yet he goes to the Ark, the place where ALL the Halos can be SIMULTANEOUSLY fired and therefore the place it would make the most sense for the Didact to be.
Then he mentions the 'great journey', we know, however, that what Didact is mentioning here appears to be wholly physical rather than the transformation into a deity. He states that he will be carrying this record and that others will know the error in the Forerunners' ways - the 'false transcendence' refers to the Mantle and the atrocity it led to.
It sounds as though the Forerunners were definitely leaving their place on the Ark, but rather than an ascending to glory, they're descending into shame and personal disgust. And, as we know, they exiled themselves beyond the orion Arm (presumably to hide from their betrayal of the galaxy through the Array, not wanting to live in the same place as the very worlds they abandoned hope on upon the Flood's arrival).
What he says toward the end of the IRIS story text seems to indicate that Didact is alive.
It's done. By my hands. The pyrrhic solution is ignited. All I have left is the quiet of space to lull me to sleep.
I will dream of you.
The Didact has already fired the Halos here. It hints strongly that when taking part in the Forerunners' Great Journey, he would exist somewhere in space, possibly in a state of suspended animation, but clearly alone now that he has lost Librarian. Again, perhaps in timeless xankara where he shall remain.
Then there's the opening of Cryptum where the Didact/Bornstellar is about to tell the story of the Forerunners, yet he is saying it in the past tense and seemingly to someone.
And there's the rather ominous end of Terminal 10 in CEA, whilst Spark is talking hypothetically, clearly the fact that the Didact plays such a prominent role in the present tense with his emblem being the last thing we see is more significant than just saying, "oh if only that dead guy was here".
I am not at all convinced that the Didact is dead, until something outright states that he is and proves me wrong, I say he's alive. Whether he performed a brevet mutation on another person or had his thoughts put in a Durance, all evidence seems to show that he's alive in some shape or form.
[Edited on 12.17.2011 3:48 AM PST]