In S05E02 of Person of Interest we saw that the Machine remembers 42 removals. But we know from previous seasons that all data was deleted at midnight.

Is there any explanation for this?

  • "all data" is clearly not true or Finch couldn't train the machine to make good judgement calls if all data were erased. There are clearly some things the machine can learn over time. But the detail of the identities of "irrelevant" people is clearly erased at midnight. It is never clear what else.
    – matt_black
    Commented Jul 1, 2016 at 17:26

3 Answers 3


The Machine was programmed to erase its memory at midnight everyday. But it has been evolving, it is always evolving. Evident by the fact it is talking to Root as an analog interface.

And its probably hiring people as seen in the ending scene, where a woman uses the same speech Finch used to hire Reese.

In Season 2 Eps 21 - Zero Day, Finch learns about how The Machine has created a fake identity and a company who hires people to re-enter data after midnight, essentially re-enter its memories.

In Season 5 Eps 2, when The Machine got access to the feeds and internet, it then deemed Finch, Root, Reese to be a treat, before that it was running ok, One can only guess that since The Machine did not have access to the history feed.

You also have to notice that The Machine makes judgement after visiting the past records/feeds/videos/data (whatever you wanna call it). And those records are not memories and hence are not deleted. So those records are probably saved somewhere.

Coming back to present, since The Machine have no number system, it probably read all the records at once and hence all the times Finch killed it.

Now you maybe asking where are all those videos saved? I have no clue. But it must be saved somewhere, as The Machine makes it judgement after watching the history.

  • But does it make sense delete everything at midnight or killling Machine by erasing it if Machine can access all that videos and see past?
    – raiym
    Commented May 12, 2016 at 12:59
  • 1
    Erasing the memory was done to stop its exponential growth, to stop it from being bigger than human beings........It does make sense, the access to videos would only give it data about the people and their behavior so that it could identify the potential crime, the videos has nothing about The Machine, or what it had/have learn......
    – j4rey
    Commented May 12, 2016 at 13:06
  • I get it now. Make sense to me
    – raiym
    Commented May 12, 2016 at 13:13

If everything the machine learned during a day were erased at midnight, the machine would be unable to learn over time. One episode shows Finch trying to teach chess to the machine, so we can assume he wanted the machine to learn new things over time. The "erase all data at midnight" rule applies only to the persons of interest the machine learns about but not to metadata, such as the process the machine uses to make its decisions (such as how to locate persons of interest).

  • 1
    In Season 5 Eps 1 or 2, it showed that the first time Finch added the Erase-All-Data-At-Midnight function, the machine even forgot about Finch and had to ask if he was admin......The whole point about Erasing-All-Data-At-Midnight was so that The Machine wouldn't be able to advance/evolve itself.....I am afraid you are wrong, The Machine not only erases the Person-Of-Interest but also its data, what it learned
    – j4rey
    Commented May 12, 2016 at 11:16
  • In the if-then-else episode in season 3 (link in answer), it shows Finch is aware that not only does the machine remember stuff over the 24 hour reset but Finch apparently has no problem with that. Unfortunately I haven't see any season 5 episodes yet; I don't get TV and am waiting for the season 5 DVDs to come out. Commented May 12, 2016 at 12:34

Imagine you having access to hundreds of books and the ability to read and understand them all in a matter of minutes. But, here is a cliche, you forget everything you have read.
This might be the case of the machine, it had the access to the feeds and internet and analysed everything daily(after its "erase all data at midnight" rule)
In S05E02 the machine had access to the feed of past and real time

but was unable to differentiate the timeline. For the machine it all felt like its happening at the same time

this can be backed up

as root says "She's falling through time.Probably a serial processing issue." Which means the machines parallel processing was working fine not the serial which explains when Finch asks "What day is it?" which is replied as R


What Finch replies solves everything "R, the mathematical set of all real numbers. Today is every day to you. I killed you 42 times. And you are constantly reliving those 42 deaths." Thus, the machines parallel processing was going through those days again and again(imagine reading same set of books reading again and again)

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