The basis is that a feel illusion should feel right, and temperature is as much a part of feel as any of the other factors like texture or resiliancy.
No temperature is not a property of the matter of item no matter how many times you keep stating it. The heat level of an item and its heat transfer to the environment is very much a physical process that is not a property of the matter of the object. The rate of heat transferred by the item is an aspect of the matter of the item, but that is something different than actual heat. The iron molecules remain iron molecules no matter if we chill or heat them. Sorry, but there is no way ever that I will agree something that my education and real world experience tells me is false.
In terms of reproduction, Heat, or cold is just a tiny tweak to the energy levels.
It takes no energy at all to passively accept the heat level of the environment. If the item should be heated you need to constantly add energy to make up for the heat loss. It is given this require some kind of added energy. There is no basis at all to say that it is a tiny tweaks of energy levels.
Go feel your wrist and hand. . . .the feel phantasm will perfectly duplicate the stifness of the bones, the resiliancy of the skin, the brushy feeling of the hair, the firm resistance of the muscle, the play of muscle and the feel of a pulse. . .All of those are far harder to do than mere warm or cold.
Why?
Because I should agree with even though you don't have any real supporting argument except that illusions must be heated because else they are not as useful as you like?
As already noted, the people sensing the effect can probably discern the illusion because of one of their other senses, and the illusion has a limited duration. The feel mirage is the most powerful, but it is a 5th level spell (as a comparison a 2nd level closed essence spell will summon a real creature for the same duration).
The feel mirage is more powerful, as it handles far more aspects. . .and you can't attack with it, you need a phantasm or strike for that. . .it's more powerful because it's the most complex of the mirages involved.
I do agree that it is more powerful. That is a very good reason why it should not also heat the object. It should require a separate heat spell just like all other non trivial aspects of the item.
There is a specific limitation that attacks are strikes handled in a particular way. . .and there are specific other factors with seperate mirages, like presence or power. . .or light.
Exactly...light require separate spells, heat and heat radiation is very much an aspect of photons too so it should need extra spells to heat the illusion. There are such spells in Spell Law and even an Illusionist can access them if he purchase a magic item. You say he does not need to since the feel spell fits the bill even though it does not mention heat at all and no example in any of the books refer to it being able to change temperature of an object. I think the spell should say "does heat the object" if it should heat the object.
But unless you want to create a lightning bug or similar light producing creature, or a lantern or light producting fire any and all objects can be convincingly duplicated using illusion/sound/smell/taste/feel 5 part combo. That's not my opinion, that's what it says in the rules:
Again...object does not equal living being. It does not say you can convincingly duplicate everything that exist below the sun or that you can convincingly duplicate processes, it says you can duplicate objects plain and simple. Every passage it totally consistent with the idea that this means normal objects and not living beings.
The only reference that might indicate something more is the discussion in gamemaster law about how much power points is needed to mimic a level 2 summons spell. I don't read that passage as strongly as you do. The illusionary beast is after all quite realistic, the only way you can spot it to be weird if you are personally familar with the excepted body temperature of the beast and get to touch it long enough for you realize that it is too cold.
The "Feel mirage" is broadly written, the highest level of the core 5 effects, and there is no "warmth mirage" provided. . .warmth/cold is necissary for feel to be convincing, the spell list states clearly, and the notes make multiple references to each of the senses being perfect enough that it's undetectable via the covered sense, requiring a missing sense to detect the fakery, and that with the 5 senses covered the illusion is in fact a temporary but real object. . .which means that any casual non damaging temperature variation necissary to make the feel element work actually exist.
The reason there is no warmth mirage might be the same as why there is no open or closed spell in the essence realm that provide heat of coldness. Creating heat is an effect that is rare in the spell system...IMO for very good reasons.
In truth the illusionary object with five senses is impossible to differ from the real thing...except if you try to mimic something that requires an process to function. Everyone agree the illusionary explosion is not believable even with five senses...the general opinion in this thread seems to be that the same hold true for the illusionary fire and the illusionary bath tube, people argue that the illusionary tent is fair game but the others are not, the question is why.
I say there is a simple line to be drawn by the fact that there is no illusion spell that provide heat. Living beings are borderline cases that in some situations are not believable and in some cases will fool the people the phantasm interact with. You argue this is not enough, you are of course free to suggest other possible limits for your setting, but it is tricky and if not careful you will end with possible loopholes that can be exploited by players.
You cannot create a convincingly real living being using phantasms without warmth, and you cannot create a convincingly real cool pool of water without coolness. . .there's no mention anywhere that "All living beings will be room temperature and thus feel wrong" or "Any object that should have a temperature variation will not, so illusions of living beings or cold objects will be fairly obviously fake if touched". . . .such hugely important matters would not have been ignored while the volumes of material about the complexity of illusions and phantasms were discussed. . .it's not like that would be a minor variation issue, that's a biggie. . .your house ruling makes it impossible to fake up a wide swath of objects using illusions, and essentially makes all living phantasms detectable by touch. . .which is so far off base of what the book says, that I have to conclude that you're simply incorect in your interpretation.
You reasoning is flawed...if the intention is that heated illusions are possible...why did they then ignore the essential discussion about to what degree illusions can be heated if they thought about the idea of heated illusions? Why did not the spell notes itself clearify this essential aspect of the spell if heated illusions is possilbe?
The absence of such discussion is easy to explain if we go with the literal normal sense meaning of spells...there is simply no way to make heated illusions since illusions mimic objects and not processes. This limitation is built into the spell lists and go without saying and that we in some situations can deduct the person is much to cold is kind of given. The failure to discuss this weak point of illusion can be viewed as a small oversight.
The reverse situation when illusions can be heated at no expense of extra power points the absence of discussions about how much heat that is possible is very hard to explain. There is no way to explain this as any small oversight, with other words there is much that speaks for my interpretation and little for yours.
Various spells state that they "create" matter, you interpret that to mean something other than "create" because you want magic in your world more in line with physics. That's fine, as a house rule. . .Whatever you want to be true is true in your game world, but that doesn't alter what it says in the books.
Get Real Get Rolemaster...if that is not your desire than so be it...but clearly I have not house ruled if I go with the literal effect of the spell but have an explanation that makes the theory of magic more consistent. That you keep insisting this is a house is quite comical.
The books allow for perfectly convincing false objects to be created via illusion, and specifically state that to be true, if you don't like that for your game, feel free to change it, but your claiming that's not what the book says is confusing.
1) Perfect illusionary objects....correct, I can read that in the books.
2)Perfect illusionary processes...nope, it does not say so...and pretty much everyone around seem to agree about it should not be possible.
3)Perfect illusionary living beings...nope, does not say so...the books only say that a level two summon spell is more powerful. To say no to 2 but yes to 3 is strange at best and a severe contradiction at worst...I think it is a contradiction of the severe kind for reasons I have already detailed.