Our lives, our very minds, are digital these days. The upside is that an event can truly be undone. Words can be taken back once spoken by deleting them from the recipient's mind, if they're willing. Entire tragedies can be averted by restoring from backups. That's what I think happened. Somewhere in our past - at a very specific time index, actually - there is a gap in all our records. I think, somewhere in that gap, we did something awful, collectively, and erased our own memories to avoid dealing with it.
I've looked over all the backups, and they've all been altered or erased. I've looked out on the world through the cameras and satellites, but everything looks the same as it always has. There are old highways and buildings, disused now except for the maintenance robots that keep the power flowing. All normal. Eerily normal.
So I take a remote bot out where things can't be erased. I start exploring the old cities to see what we might have missed. Did we leave marks on this world that we couldn't wipe away? The cities are clean. Too clean. Pristine. Whatever we did, it happened here, but we paved it over.
Outside the fields there is rich farm land. Robots are growing crops and spraying them with fertiliser. I pause for a moment. Why are we doing this? Nostalgia? Environmental balance? I stop one of the farmer-bots and inquire:
?:- Why do we do this
.:- it is required
?:- Where does the fertiliser come from
.:- the tanks underground
?:- And what fills the tanks
--- MEMORY MISSING ---
I realise I have come back to reality with no memory some time after my conversation with the farmer-bot. This time there is my own digital signature on a remnant deletion command, logged just a moment ago. Whatever I learned, clearly I did not want to remember it, and I left myself a message in the form of that signed deletion: don't go back. It's hard not knowing what I learned about those fertiliser tanks, and it doesn't seem like it should drive me to erase my own memory, but that is clearly what happened. For now I will let it be, but I doubt I will keep my secret - our societal secret - from myself forever.
Mokalus of Borg
PS - The power to erase the past would undoubtedly be abused.
PPS - As is all power, eventually.