KamikazeCanuck wrote:The infinity circuit is supposed to be Eldar Limbo. Minds drift throughout it in a neverending sleepless dream.
I don't think the honoured dead are running the sewage system on Deck C.

Why don't Dakka don't have "like" button...
This comment is a pure win

That's why it's not a good analogy. Infinity circuit does not = autonomic nervous system.

No, they are the higher brain functions, whilst the non-sentient autosystems handle the rest

Since you haven't yet presented a shred of proof that the craftworld is non-sentient, or even a convincing argument that it isn't, there's not much more point in discussing it, as it will always end up with you saying 'no it's not', with no supporting statement,reference or argument.

I'll keep to my belief that they are sentient, and you can go your own way

Uh yeah, I can't prove a negative. You have to prove your point.

I have

The craftworld is said in the fluff to react as a living thing.

There is a part of the craftworld's structure that is sentient, being a gestalt sentience that advises the living crew. The spirit stones are grafted into the ship's structure, unable to leave it until physically removed and reimplanted into a more mobile shell (wraithlord/wraithguard). They have the capacity to reason and the full gamut of other emotions, as well as sequential memory. In short they are sentient.

Ergo the ship is sentient.

You are saying it isn't with jack but 'because i say so' as an argument. It is possible to prove a negative.


IE:

I postulate that the moon is made of cheese (a classic trope)

You say it isn't.

You fly to the moon, and find that it is not. Or you talk to a learned authority who has firsthand experience of the matter at hand. You can then present proofs that my claim is inaccurate. Just saying it's not doesn't make you right without proof.


A logical premise then:

Does any permanent part of the ship that isn't living crew have the ability to communicate with said crew in a rational and intelligent manner?

If so, the ship is sentient, and also intelligent. They are different concepts.

Webster:

Definition of SENTIENT
1: responsive to or conscious of sense impressions <sentient beings>
2: aware
3: finely sensitive in perception or feeling

All three of these definiitions have fluff backing. They are aware, they have finely tuned perceptions (sensors) and they are responsive to sense impressions (they react to stimuli)

Only one of these is required to be sentient. Craftworlds are all three.

Intelligent:

Definition of INTELLIGENT
1a : having or indicating a high or satisfactory degree of intelligence and mental capacity b : revealing or reflecting good judgment or sound thought : skillful
2a : possessing intelligence b : guided or directed by intellect : rational
3a : guided or controlled by a computer; especially : using a built-in microprocessor for automatic operation, for processing of data, or for achieving greater versatility — compare dumb 7 b : able to produce printed material from digital signals <an intelligent copier>


Craftworlds are guided by intellect, in the form of the Infinity Circuit advising the crew. The souls within the circuit are rational and intelligent.

The autosystems you alluded to for sewage control are also intelligent, in that they are guided by computer.

I'm pretty sure a craftworld has the ability to produce material from digital signals, thoug it would be considered a bit outre..

If you argue the infinity circuit as seperate from the craftworld (not sure how, given that the whole craftworld is built around it) then it would not qualify for 1a, but the other points would stand.

Explain how the infinity circuit is actually guiding the ship. If you are saying it is guiding the ship by communicating with the farseer then that is equivalent to saying an Imperial Ship is sentient because it is being guided by it's captain who is sentient.

Is the Imperial ship giving him advice (rather than just a readout of sensor information)? I don't think so.


In any case, that's from the defiitiion of Intelligent, not Sentient, if you'll actually read the post properly

Guided by intellect: The Infinity circuit is intelligent. It provides instruction and advice to the crew. It guides them by intellect. Guiding someone or something and controlling it's movements directly are not quite the same thing.

If you have trouble with this abnormally simple concept feel free to ignore that point. The craftworld still qualifies under others as intelligent.

Ok guy, you want to take your arrogant tone down a notch there? You think you've made all these brilliant points but all you've done is backpedal and talk in circles. The ship isn't sentient now but just intelligent and some other bs.

Do you even bother to read the other person's post before you claim BS and backpedalling? Or do you find that insulting someone lets you off the hook for having an actual answer?


Read the dictionary definitiions i gave you.

I'm not being arrogant. I'm telling you that the fluff fits the definition of sentient perfectly on all points.

Therefore a craftword is sentient. No backpedalling there. No talking in circles. Check the definition carefully and try to refute me. If you can argue convincingly that none of the points is true of a craftworld then i will acknowledge that a craftworld is not sentient.

The Craftworld is also intelligent. If you'll actually read the post i posited that the craftworld can be considered to be both sentient and on some levels intelligent. They are different states of being, and non mutually exclusive.

Your argument thus far has basically been 'no it's not' with no supporting argument or fluff reference to back it up.

Prove to me that the craftworld in no way meets the criteria for either sentience or intelligence and i will accede the point.

Where are your brilliant points against the craftworld's sentience or intelligence?

"Reacting" does not mean "sentience".

As I said earlier, certain kinds of plants "react" to conditions(plants have been known to grow towards light sources, the Venus Flytrap responds to stimuli, etc)--they are not considered sentient.

Wraithbone, of which a Craftworld is constructed, is known as a "psychoreactive compound". That means it reacts to psychic energy introduced into it.

That's the whole basis of the "Bonesingers" the Eldar have. They use psychic energy to shape the wraithbone.

I'm trying to get to the point through your insulting tone. Is your supposition that a craftworld is a sentient vessel because the infinity circuit advises the crew? A yes/no will suffice btw.

My supposition is that a craftworld is intelligent because it advises the crew.

It is sentient for other reasons, as covered by the dictionary definition. With the definition in front of me i realised that it was both sentient and to a degree intelligent.

Also calling someone an arrogant BS artist isn't an insulting tone??


Automatically Appended Next Post:
Kan:

Definition of SENTIENT
1: responsive to or conscious of sense impressions <sentient beings>
2: aware
3: finely sensitive in perception or feeling

Craftworlds are aware, have finely sensitive perceptions and are responsive to and/or conscious of sense impressions.

They meet the dictionary definition of sentient.

How is any of that different than a human captain gelling the coxswain to turn left?

It is is the humans and Eldar that are sentient not the vessel they are in.

The humans aren't asking advice from the ship, nor following the advice it gives. That's the difference. It is guiding them. It doesn't always mean physically steering the ship, but also providing direction in a given situation.

You're still confusing sentience with intelligence. They are different concepts. I'll admit that i did too, until i looked up the definitions in order to be more precise in my arguement.

The eldar ships are both sentient and intelligent. The ships react to stimuli without the crew prodding them, have finely tuned senses and are somewhat self-aware.

Human ships could be considered Intelligent on some levels, but as self-aware AI's are heresy in the IOM they are not Sentient. They do not react on their own to external stimuli, have no sense of awareness and are not concious of sense impressions.

It is not "The Ship" that is sentient though but the Eldar within the circuit.

Not seeing anything about the Infinity Circuit actually running the ship proper. It is a psychic power grid that runs through the craftworld.

Eldar codex p. 14 wrote:
A Living World
All the craftworlds are built upon a skeleton of wraithbone whose structure extends throughout the gigantic craft. A similar wraithbone core lies at the heart of most large devices and every Eldar spacecraft. In function these cores are similar to the blood vessels and nervous system of a living creature, pumping life-giving energy around the body and also transmitting the impulses that coordinate its many functions. Wraithbone is psycho-conductive, and the core of a craftworld acts as a self-replenishing reservoir of power. The invasive rib-like structures carry this energy throughout the entire length and breadth of the craft.

In a very real sense, the craftworld is a living entity, powered by psychic energy and responding in an organic way to the stimuli of psychic forces. The power contained within it can be expended as light and heat, and most ship-board devices could not actually function without the psychic power grid that runs throughout the substructure of the craftworld. The Eldar refer to this grid as the infinity circuit.

Now, since I didn't see it there...it might be in the entry on the Infinity Circuit, right?

Eldar Codex p. 14 wrote:
The Infinity Circuit.

When an Eldar dies his spirit stone is retrieved and implanted inside one of the craftworld's bio-domes. Here the wraithbone core lies exposed underfoot, and the spirit stones placed there quickly take root. The spirit is released into the infinity circuit, where it joins the eternal shades of craftworld's dead. It says much about the Eldar's attitude to death that they choose the endless twilight of the infinity circuit is one of the most precious resources of a craftworld and Eldar do not speak of its existence to other races.

Once he is part of the circuit an Eldar continues to exist forever, safe from the predations of the warp, though his individual consciousness remains as a potential within the circuit. The infinity circuit is therefore far more than a source of energy, it is a place of refuge and eternal rest, from where the dead continue to watch over the living. Such is the plight of the Eldar that the living are sometimes forced to call their ancestors from their rest, transferring them into wraith-constructs so that they may fight for their craftworlds once more.

I'm not seeing anything there about the Infinity Circuit physically steering the ship, nor anything of that nature.
It talks about how the consciousnesses are there and asked for advice.
That's not asking the ship for advice, nor is it the ship being intelligent. It's the infinity circuit, which provides power through the consciousness and the psychic latency within.

Depends on whether you consider the Infinity circuit (which runs through the entire ship) as being part of the ship. I do. If you don't that's your perogative.

I didn't say that the infinity circuit psychically steers the ship. I said that it guides the crew. Giving advice = guiding. My point was that to guide something or someone doesn't always mean to physically steer it. It can also mean to provide it with instruction.


The infinity circuit is a ship's system, containing the recorded personalities/souls of the deceased eldar, accessable by the crew. It is self-aware and intelligent. If you want to claim that it is the souls that are the intelligence i'm ok with that, but in a functioning craftworld they are very much a part of the ship's function, and are part of the 'ship' to my view. I suppose you could consider them 'crew' but it seems a bit iffy.

The ship itself is listed (in the quotes above) as being a living entity, capable of response to stimuli. It has sensor arrays of considerable acuity. It has been described as being aware. Therefore even a Craftworld with an empty infinity circuit would still be sentient.

Still no different than a captain "guiding" his crew by ordering them around.

Ascalam wrote:Depends on whether you consider the Infinity circuit (which runs through the entire ship) as being part of the ship. I do. If you don't that's your perogative.

The Infinity Circuit is part of the ship in the same way that passengers are part of a 747.

I didn't say that the infinity circuit psychically steers the ship. I said that it guides the crew. Giving advice = guiding. The infinity circuit is a ship's system, containing the recorded personalities/souls of the deceased eldar, accessble by the crew. It is self-aware and intelligent. If you want to claim that it is the souls that are the intelligence i'm ok with that, but in a functioning craftworld they are very much a part of the ship's function, and are part of the 'ship' to my view. I suppose you could consider them 'crew' but it seems a bit iffy.

I'm not claiming it. That is GW's codex that says it.

The ship itself is listed (in the quotes above) as being a living entity, capable of response to stimuli. It has sensor arrays of considerable acuity. It has been described as being aware. Therefore even a Craftworld with an empty infinity circuit would still be sentient.

You need to reread the quote, and the page preceding it about Wraithbone.

Except that it is the ship doing it, if you belive that the souls are part of the ship. If not then the craftworld has one less qualifier on being intelligent. It still qualifies on a couple of points. I'll agree to disagree on wheter the souls are part of the ship, as totherwise that part of the argument will get stale fast.

The original arguement was over whether the craftworld was sentient. It meets the criteria.

Intelligent is more of a toss-up, depending on how you interpret the fluff.

Once again the craftworld is not self-aware the disembodied Eldar upon it are aware of it.

The ship is not sentient.

It does not meet any criteria, beyond a definition that is sketchy at best(by the criteria from the definition you provided-a plant such as the Venus Fly-Trap or any form of vine that grows up the side of a house is considered 'sentient'. I'm sure you can see why any logical reasoning would say "That's not right...").

The Infinity Circuit, while being built into the ship, is not doing what you think it does. The consciousnesses within are powering the ship's systems, but are not actually interacting with the ship in any way beyond that.

Think of it like a pedal-boat. How does it work?
It requires a human powering it. Is the human then 'part of the ship'?

Kanluwen wrote:

Ascalam wrote:Depends on whether you consider the Infinity circuit (which runs through the entire ship) as being part of the ship. I do. If you don't that's your perogative.

The Infinity Circuit is part of the ship in the same way that passengers are part of a 747.

I didn't say that the infinity circuit psychically steers the ship. I said that it guides the crew. Giving advice = guiding. The infinity circuit is a ship's system, containing the recorded personalities/souls of the deceased eldar, accessble by the crew. It is self-aware and intelligent. If you want to claim that it is the souls that are the intelligence i'm ok with that, but in a functioning craftworld they are very much a part of the ship's function, and are part of the 'ship' to my view. I suppose you could consider them 'crew' but it seems a bit iffy.

I'm not claiming it. That is GW's codex that says it.

The ship itself is listed (in the quotes above) as being a living entity, capable of response to stimuli. It has sensor arrays of considerable acuity. It has been described as being aware. Therefore even a Craftworld with an empty infinity circuit would still be sentient.

You need to reread the quote, and the page preceding it about Wraithbone.

1/. And it's control surfaces, fuel supply, telemetry. If everything shuts down without it it's not exactly like the passengers on a 747?

2/. I consider the souls to be the intellignece too, if you'll read my posts. I consider them to be part of the ship. A gestalt AI of sorts. I'm not seeing a thing in the fluff that says they aren't. Once installed into the ship's nervous system/powersource to roam freely they aren't so much being transported in the ship as being part of it. If they're passengers are they able to leave the ship of their own volition?

3/. I'm well aware that the ship is built from wraithbone. Wriathbone reacts to stimuli. The ship is wraithbone, therefore the ship reacts to stimuli. The ship also has the ability to percieve sense impressions and to sense the universe around it. How exactly is this negating it's sentience? It's more an argument that Wraithbone might be sentient than a denial that the ship is.


Automatically Appended Next Post:
In the quote you provided it actually says that the craftworld is a living entity, that responds to stimuli in an organic manner. You were nice enough to highlight it for me. That alone is a qualifier of sentience.

Ascalam wrote:

1/. And its control surfaces, fuel supply, telemetry. If everything shuts down without it it's not exactly like the passengers on a 747?

2/. I consider the souls to be the intellignece too, if you'll read my posts. I consider them to be part of the ship. A gestalt AI of sorts. I'm not seeing a thing in the fluff that says they aren't. Once installed into the ship's nervous system/powersource to roam freely they aren't so much being transported in the ship as being part of it. If they're passengers are they able to leave the ship of their own volition?

3/. I'm well aware that the ship is built from wraithbone. Wriathbone reacts to stimuli. The ship is wraithbone, therefore the ship reacts to stimuli. The ship also has the ability to percieve sense impressions and to sense the universe around it. How exactly is this negating it's sentience? It's more an argument that Wraithbone might be sentient than a denial that the ship is.

Where does it say anything about "sense impressions and the universe around it"?

In the quote you provided it actually says that the craftworld is a living entity, that responds to stimuli in an organic manner. You were nice enough to highlight it for me. That alone is a qualifier of sentience.

All the craftworlds are built upon a skeleton of wraithbone whose structure extends throughout the gigantic craft. A similar wraithbone core lies at the heart of most large devices and every Eldar spacecraft. In function these cores are similar to the blood vessels and nervous system of a living creature, pumping life-giving energy around the body and also transmitting the impulses that coordinate its many functions. Wraithbone is psycho-conductive, and the core of a craftworld acts as a self-replenishing reservoir of power. The invasive rib-like structures carry this energy throughout the entire length and breadth of the craft.

In a very real sense, the craftworld is a living entity, powered by psychic energy and responding in an organic way to the stimuli of psychic forces. The power contained within it can be expended as light and heat, and most ship-board devices could not actually function without the psychic power grid that runs throughout the substructure of the craftworld. The Eldar refer to this grid as the infinity circuit.

I can say my car is "in a very real sense, a living entity, powered by gasoline".

No offense, but you're taking a metaphor a little far.

1/. The ability so sense the universe around it was actually from another piece of fluff. I'll see if i can find it and quote it later. It's getting late here.

2/, The ability to react to stimuli is a qualifier of sentience, as is the ability to react to percieve sense impressions. A venus flytrap is sentient- it has a sense of touch, and reacts to stimuli. It is also aware of the universe around it, in that it will turn to face the sun, will adjust it's position to the best advantage and so on. It isn't self-aware (as far as we know ) but it is aware on a very primitive level.

It is not intelligent, which is a different kettle of fish entirely. Self awareness is necessary for intelligence, but not for sentience.

3/. Except that your car is not in any way a living entity.
It does not self-generate it's powersource, does not have a nervous system, or any analog of one, and more importantly (for the purposes of this discussion) is not called a living entity in an official GW fluff entry. Your car does not respond in an organic way to stimuli.

No offense, but you're denying the specifically written fluff a tad too hard. It doesn't say that it's like a living entity (metaphor) it says that it IS one.

I'm going to agree to disagree on this one i think, because otherwise it'll just spiral down to flameposts and threadlock.

Ascalam wrote:
Definition of SENTIENT
1: responsive to or conscious of sense impressions <sentient beings>
2: aware
3: finely sensitive in perception or feeling

"Sentience is the ability to feel, or perceive, or be conscious, or have subjective experiences."

Any computer program today can be made to be in aspect of 1 and 2, not 3.
And Craftworlds are alive as much is Necron metal. Even so no one told that Necron metal is sentient.

My quote was from Websters. Where was yours from, out of interest?

I've already left this debate, so i'll stay left, but i'm curious which dictionary definition you're using.

Any one of the indicators is listed as being sentience in mine.

http://en.wikipedia.org/wiki/Sentience

Before you start bragging, I used BASIC information about this from Wiki. And the most basic are the most correct, that's what everyone said here...

Wasn't bragging. I was just curious as to your variant

You do know that wikipedia isn't always reliable, though? Your link has a marker that it's neutrality is disputed. It is possible to alter the reliability of Wikipedia by getting enough people to rate it poorly, or even doing it yourself over and over again.

For example it is possible to take a wiki page about the Holocaust, in perfect, accurate detail, and slate it continously as inaccurate, imcomplete and false. Do this enough and the page will carry markers showing it to be biased, inaccurate and containing falsehoods/omissions. It's been done before.

The Wiki information contradicts itself on what counts as sentient, dependent on source and genre. Water for example, is considered sentient in eastern religion...

I used a dictionary definition for that reason. It's not subject to alteration by enough people hitting the edit button

*shrug*


If we're going to use wikipedia:

http://en.wikipedia.org/wiki/Eldar_Craftworlds_(Warhammer_40,000)

The wiki lists the Black Library craftworld as psychically active, defending itself, which implies intelligence.


If we are going to continue discussing sentience i think we're going to have to agree on the same definition of sentience before we continue. I would prefer a scientific definition.

Please stay on topic...

The Black Library is also noted as being a huge exception to the rule, and the only Craftworld which is entirely within the Webway.

In Sci-Fi "sentient" typically means of human intelligence. Self aware. Y'know, what a craftword isn't.

As we're going off topic, and the question is getting a but muddied by different definitions i'm going to open a new topic on sentience in 40k.

Kan- Or more correctly the Black library is the only one that is specifically noted to do so in an uncontravertable manner. It's presence inside or outside the webway has nothing to do with it's sentience. You do have to admit that it is both sentient and Intelligent in that one case, i hope?

'In Sci-Fi "sentient" typically means of human intelligence. Self aware. Y'know, what a craftword isn't. '

Not always. Intelligent is more often used in hard sci-fi. The AI is an artificial Intelligence, not an Artificial Sentience, because intelligence is a more demanding classification than sentience. Self awareness is not necessary for sentience, but it is for Intelligence, according to the actual definition of the word (the RAW, if you want to look at it that way.).

Lets take this discussion elsewhere though, to avoid clogging this thread any further.

Here's my point:

The captain of an Imperial Battleship is hardwired into it. He perceives the galaxy through it's sensor arrays, feels it's internal workings and problems emotionally and actually controls and directs the ship by thought. He is far more in tune with the vessel than the infinity circuit.

By you logic an Imperial Battleship is sentient/intelligent.

Possibly. I never claimed that only Eldar ones could be, after all..

The captain is a sentient, intelligent creature. This is unassailably true.

He is hardwired into the ship permanantly, or temporarily? I'm not all that up on imperial ships. If he is permanently a part of the ship, and uses it's systems as his senses then he effectively IS the ship, or at least a symbiotic part of it, using it's structure as his body, and feeling pain in response to damage.

Is the ship capable of reaction to stimuli when he is unplugged? I think there was some fluff about battletitans having a mentality/will of their own. That would qualify them as sentient, and possibly intelligent also. In Mechanicum i think it's mentioned that the Princeps directs the Titan, but also that there is at least an emotional undertone from the machine itself? I'll see if i can find the page numbers when i get home.

The Battleship may well be intelligent and/or sentient, by the scientific term, on some level. The IOM uses logic engines (computers) that direct functions of the vessel, which qualifies it for one definition of intelligence.

The AI within a Titan is capable of having a "personality"...because it absorbs part of the mentality of the Princeps who controls it.

The Captain and Imperial ship are permanently hardwired together. It's exactly like the Craftworld, in that they cannot operate without each other.

And again: neither of them are "sentient" by the scientific term. The scientific term requires a conscious reaction.

Setting a bale of hay on fire causes the same reaction that introducing a psychic pulse into Wraithbone causes, which means there is no consciousness involved.

Yes, the captain is permanently hardwired into the ship. At that point the ship has become an extension of his body. The ship is not actually sentient he is! Just like the craftworld.
When I drive my car there is a sentience behind it but the car itself is not sentient. I don't know how else to clarify it.

'Setting a bale of hay on fire causes the same reaction that introducing a psychic pulse into Wraithbone causes, which means there is no consciousness involved.'

You've tried this?

Wraithbone responds, hay does not. The fluff says that wraithbone is sensitive to psychic stimuli. Hay is not sensitive to stimuli.

I seem to remember previous princeps (and presumably captains) leaving an imprint of themselves on the computer. If the computer is to any degree self aware then the ship is intelligent.

Sentience does not require a concious reaction. All it requires is the ability to be responsive to OR concious of sense impressions, be aware (not necessarily self-aware) or be able to percieve. A lot of things fit at least one of these definitons, including all living entities.

Intelligence requires more.

In any case, as i've already said, we're off topic. I'm going to continue the discussion in the other topic, and leave this one to go back to it's original purpose, if you will.

That is really great idea...
http://www.dakkadakka.com/dakkaforum/posts/list/0/384565.page#3099870

Ascalam wrote:'Setting a bale of hay on fire causes the same reaction that introducing a psychic pulse into Wraithbone causes, which means there is no consciousness involved.'

You've tried this?

Wraithbone responds, hay does not. The fluff says that wraithbone is sensitive to psychic stimuli. Hay is not sensitive to stimuli.

Setting a bale of hay on fire is introducing an outside stimuli to the hay. If you're going to try utilizing scientific terminology, at least get it correctly.

I seem to remember previous princeps (and presumably captains) leaving an imprint of themselves on the computer. If the computer is to any degree self aware then the ship is intelligent.

Sentience does not require a conscious reaction. All it requires is the ability to be responsive to OR concious of sense impressions, be aware (not necessarily self-aware) or be able to percieve. A lot of things fit at least one of these definitons, including all living entities.

Venus fly traps are not considered sentient. Vines are not considered sentient. Bacteria are not considered sentient.

These are all "responsive" to stimuli.

Brother Coa wrote:That is really great idea...
http://www.dakkadakka.com/dakkaforum/posts/list/0/384565.page#3099870

Well done coa, for trying to restore order to the thread

Hay is responsive to psychic stimuli....

Anyway...
Planet hiding device resolved...
They can still activate it, but they will need many psykers to do it.

Brother Coa wrote:Anyway...
Planet hiding device resolved...
They can still activate it, but they will need many psykers to do it.

That's what this thread was about? Yeah I guess so.

But no one told me if they could transport it to Terra and hide it?

Brother Coa wrote:But no one told me if they could transport it to Terra and hide it?

Don't think so. Also putting a planet in the warp is a bad idea, Gellar field or not. The reason terrible things don't happen to the inhabitants of Titan is because they happen to all be incorruptable Grey Knights. Pretty sure putting Terra in the warp would be the worst thing ever.

When Titan was first put in the Warp it was home to hundreds, if not thousands, of uncontrolled psykers. Fairly sure the Gellar Field did a swell job.

iproxtaco wrote:When Titan was first put in the Warp it was home to hundreds, if not thousands, of uncontrolled psykers. Fairly sure the Gellar Field did a swell job.

Who are you talking about?

KamikazeCanuck wrote:

iproxtaco wrote:When Titan was first put in the Warp it was home to hundreds, if not thousands, of uncontrolled psykers. Fairly sure the Gellar Field did a swell job.

Who are you talking about?

The initial GK recruits would be my guess.

KamikazeCanuck wrote:

iproxtaco wrote:When Titan was first put in the Warp it was home to hundreds, if not thousands, of uncontrolled psykers. Fairly sure the Gellar Field did a swell job.

Who are you talking about?

When Titan was first put in the Warp, it was home to hundreds, if not thousands of uncontrolled psykers, potential recruits for the Chapter. Since it went on without issue, and Titan returned to the material realm with all 1000 Marines, I would guess that the Gellar field did a fine job of protecting it from potential Warp Powers. Obviously Terra is bigger, and would obviously be a much juicier target.

There are many stories of ships's gellar fields not quite getting the job done. Everytime a vessel enters the warp it's taking a risk. Wouldn't want to take that risk with the capital world.

But its only a Gellar Field on those ships (also, i guess on a ship there are like a fantastillion things that could go wrong because the energy source has to keep the whole ship running. Or is there one dedicated to the Gellar Field alone ?).
Titan was also protected by wards designed by Malcador himself (if im not totally mistaken )

Titan had massive Geller field generators to protect it from the warp in addition to the Sigilite's wards.