The Flood is a non-sentient life form. That's why the Halo array is unable to kill it directly (the Flood is starved to death which is passive killing by Halo).

What I see about the Flood in the video game franchise:

  • They recognize and attack all of their enemies; not just their food (sentient lives: humans, covenant), but also the Sentinels of 343 Guilty Spark.
  • They handle advanced weapons like Plasma Guns, Shotguns, Rocket Launchers etc. Interestingly, they don't miss their target most of time.
  • They operate advanced vehicles (of humans or covenant) very efficiently in coordination with other Flood beings.
  • They create advanced plans to capture a spaceship so they can leave Halo.
  • They fight with advanced team strategies.

How does they do all these things? Is there an intelligent collective or something similar for that?

  • 10
    I think you would be amazed by a Biology class :) Real-life cells are able to do many amazing things automonously (ie. without sentience), such as recognize and attack foreign cells, navigate complex systems, and coordinate to build and repair large structures (like your body). Even further down, proteins (especially enzymes) are capable of equally amazing things, and they are not even considered alive. And, further up, there are some seemingly-sentient animals which don't have brains (Jellyfish, for example). Commented Nov 26, 2012 at 21:05
  • @BlueRaja If you watch those microscopic systems closely, everything works based on some sort of physics or chemistry. Affinity towards this, permeability towards that. In that world, choice isn't involved. That's why the logic can't be applied for macroscopic actions like shooting plasma guns where there're many choices and other things. That's why sentience is required.
    – user931
    Commented Nov 26, 2012 at 21:14
  • 3
    A large number of scientists would argue that, at the lowest level, "sentience" also boils down to just physical/chemical interactions. But even if it didn't, I don't see how your conclusion follows. Who says Jellyfish can't evolve to use plasma guns? Commented Nov 26, 2012 at 21:18
  • @BlueRaja Macroscopic sentience isn't simply physical-chemical interaction, not matter its built with that.
    – user931
    Commented Nov 26, 2012 at 21:23
  • 1
    Anyone interested in that question, I highly recommend [Blindsight](en.wikipedia.org/wiki/Blindsight_(Watts_novel) by Peter Watts (alas, now out-of-print). It addresses the question of how self-awareness and intelligent problem-solving, are related (or possibly even in conflict).
    – John C
    Commented Feb 24, 2013 at 13:18

2 Answers 2


According to Halo Nation, the Flood move through several stages. At the basic stage, the "Feral Stage", the Flood is

only capable of local coordination through use of pheromone-based communication. Research indicates that the content of said messages are of very limited complexity. Individual Combat and Carrier Forms have access to the skills and memories of their host

This is the stage we see the Flood in during the events of Halo: Combat Evolved. It is only upon the reaching of the "Coordinated Stage", where a proto-Gravemind is formed, that the hive mind begins to work together on a wider level. We see this at the very end of Halo: Combat Evolved and in the Last Voyage of the Infinite Succor.

Once the Flood forms a full Gravemind, a "central compound intelligence", near omniscience is achieved, and full control is maintained over all Flood specimens. It is at this point that the Flood becomes very dangerous, as the Gravemind is capable of organizing strategic-level assaults.

Presumably the plans to leave Installation 04 in Halo: CE are the results of the proto-Gravemind's machinations. As to what level of detail individual Flood forms are able to coordinate, that is unclear.


The Flood in Halo: Combat Evolved are thought to have a hive mind able to assimilate the knowledge of their targets after they are taken over. In the graphic novel, 'The Last Voyage of the Infinite Succor', the Flood's true nature as a mutable, intelligent threat is revealed.

Lee Hammock, writer of 'The Last Voyage of the Infinite Succor', described the basis of the story as a way to showcase the true danger of the Flood as an intelligent menace, rather than something the player encounters and shoots. Hammock also stated that the story would prove the intelligent nature of the Flood, and "hopefully euthanize the idea that they are just space zombies".

  • Means, they use nervous system of host. Right?
    – user931
    Commented Nov 26, 2012 at 16:43
  • Most likely, they would have to take over the autonomic functions of any host body they are trying to use. This probably facilitates them learning about how to use the technology as well. Commented Nov 26, 2012 at 16:47
  • Yes, they take over the host's mind, extracting memories. This enables them to use machinery and technology to facilitate their expansion
    – The Fallen
    Commented Nov 26, 2012 at 17:10

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