That is the biggest secret of the free-masons... So don't go around telling people 
That's attractively simple, but I wonder. There's no natural way to, say, move a cloud off of the path the winds dictate for it. But I wouldn't like to think that a cloud's trajectory was essential to the cloud. Likewise very, very large rocks: surely Europe could have been a few miles farther from Africa, but just as surely, it's not naturally possible to move it. ("Can God make a rock too heavy for magi to lift?")
Perhaps the rule would work for muto spells, specifically?
A cloud can be naturally moved (by the winds), so they can be affected by magic.
Also remember that it is permanent change that is impossible (with Hermetic magic). Non-permanent changes can be done without too much trouble. As I've understood this, Muto is the technique of altering EN (temporarily).
Aristotle is all very well, but if you go a bit further back to Socrates (or at least Plato) you'll find the myth quoted in THE SYMPOSIUM that men and women were once part of a single hermaphrodite creature that was forcibly split apart and that we're all looking for the corresponding part of ourselves we are missing, through many lives and many incarnations...
my two cents...
I think a maga that wanted to be a magus, but had to steal sperm to reproduce has a lot more story potential than one that is just all male after the effect.
Even though my companion Karlotte is determined to produce an heir without getting married or sinning (true faith, you see)
....hmmmm....
Questions:
- Would ReCo'ing some unwitting guy's sperm to cause a pregnancy be a sin? Probably.
- Can one produce an heir by other means? Is adoption enough to produce an heir for a landed noble?
- She is also a combat-oriented character (Karlotte is complex). I wonder what the game effects of pregnancy would be on her?
As a follow up, here are my suggestions for handling character pregnancy in Ars5.
Please note: I am male, my wife has never had a child. If there are any mothers on this list, I would love to hear their comments.
Well it lasts three seasons. At any time during the pregnancy, if the mother is injured, she must make a Stamina roll against the amount of damage to avoid losing the child within a day.
Season one: The mother must make a Stamina roll at 6+ to avoid vomiting whenever the SG thinks it would be appropriate. Stressful and fatigueing situations are good.
Season two: Mother should be showing by now and in addition to the above, receives a -1 to Stamina temporarily.
Season Three: The mother now also has a -1 to any rolls involving moving quickly or gracefully (this is like a minor version of "Obese").
Giving Birth: Birth does a stress die of damage to the mother.She still has to make the roll to avoid losing the child during childbirth.
CrCo can be used to give bonuses to the stress rolls to not lose the child the same way they can be used to improve recovery rolls.
what about this:
- use the mystery virtue (inscription on the soul i think) which do your soul be your talisman
- enchant it with a muco for sex change with sun duration, and environnemental trigger (sunset/rise)
- enjoy!
For me, it seems it doesnt break the essential nature because the effect isn't constant... : it's just constantly renewed 
Arts and Academe does a good job of dealing with the birthing process. For the actual pregnacy:
First trimester: Starting about 3 weeks in until 8-9 weeks, there should be a check upon weaking up for the morning sickness. Outside of that, there should be little impact. Hard blows to stomach should have impact and danger but othewise not much else. IT does not strike every one equally though, some have no morning sickness. The stamina roll when first waking up each day should probably be stamina diff 3 (it is more queasiness than throwing up in general)
Second trimester: the -1 is not really the correct roll. The body actually adjusts well to pregnancy and tends to thrive some. It just tires faster. I would say basically any time they would get a long term fatigue level, stamina vs 6 to avoid a second. Every time they get a short term fatigue level, stamina vs 6 to keep it from being long term.
Third trimester: Season 3, Same effects as season 2 + the obese effects + periodic rolls during day for misc effects (food cravings, frequent bathroom trips from bladder pressure, kicking). EVery morning after the 8th month starts: Stamina vs 3 + (number of days into month/3) or go into labor.
EDIT: Removed cause I fail at noticing there were multiple pages.
EDIT: Removed for the exact same reason.
Go figure. 
I've considered turning animals into humans with Muto for a period and breeding them. Mostly for fun.
If your Saga is one where God actually controls souls with an uncontested Divine Realm, unlike ours, He might well decide they might end up with actual souls instead of Faeries/Demons/Dead. Heck, even if he isn't in control.
I don't see any reason why a man turned into a woman with Muto for the entire period couldn't bear children. After all, in every other situation, she'll react physically exactly as she is. The only thing that might conceivably prevent it is the Ultimate Copout, divine action.
Sure, Essential Nature is important, but isn't Muto a sort of temporary suspension of it? Your Essential Nature as a human isn't influenced when you get turned into a frog, but that doesn't prevent you from croaking like one. A human turned into a fire will consume wood like any fire. The only way reproduction could be limited is if you decide that it's a sacred thing that only the Pantokrator has control over; Art and Academe even goes into detail to show a very non-godly process (and then there's that side bar about the maga who made people in a vat.)
Seems to be taken for granted that such kids'll be demon/fairy/undead however...
Never happened here, but I would say that sex change / animal species change creates a being that is sterile. YMMV
Cheers,
Xavi
There are several, at least, that jump immediately and easily to mind.
One is, of course, saga considerations. If it hurts the story, or it could, conceivably, hurt the story, it's out. But that should be a given for almost anything, including some of the RAW.Let's take this to one logical, extreme conclusion. It's conceivable for a mage to clone themselves - not with all their power, but the body at least. Perhaps even to split themselves into two separate beings for a short period of time. It would then be simple to change one to the opposite sex, and impregnate themselves, and conceive and bear their own child - and be both mother and father. If that works for you, great...
The more directly relevant reasons might be drawn from the Limits of Magic. Human childbirth is not mere biological mechanics, some lab formula that "1 male + 1 female = offspring"; it's far more than that in ME (especially where "humans" are concerned!). And remember, we're dealing with "magic" here - it doesn't have to make perfect and intuitive sense and follow modern logic - in fact, magic probably will not more often than it does.
Limits of Magic:
While treating male/female in purely mechanistic terms is fine, in ME they are more complex than that. "Women" are, in their Essential Nature, the child-bearers, and there is something mystical and, dare I say, magical in childbirth, especially human childbirth. To compare it to the whelping of mere animals, the breeding of kine, is a purely modern heresy.
(And someone asked "why" a man must be male in their essential nature, & similarly with a woman. They don't, but without a Virtue/Flaw that implies- nay declares otherwise, they are not assumed to be undefined. It would be beyond "rare" for a person of one apparent sex to be, by their Essential Nature, of another sex, at least in ME. imo, ysmv, offer not valid in New Jersey.)
Further, such a magical childbirth might break the Limit of Creation. The act of childbirth is, literally, the act of creation, and to effect such via magic, directly or indirectly, seems to be a breech of this basic concept, to permanently create something (a living human being!) via magic without vis.
It could also be convincingly argued that the birth of a human child is "a miracle", even if a commonplace one, and that some unexpected Limit of the Divine does not allow it. This is not "divine intervention", but actually a Hermetic barrier to the act, to preclude magi from duplicating divine acts. And what is more divine than childbirth? (Limit of the Soul may or may not be tied in here - just another possible reason. in the growing list.)
And you're comparing the production of a human life with the production of a croak?
In a word - "No" - there is never a "suspension" of the laws of Magic, "sort of" or otherwise, and, with all due respect, if you think there is I strongly suggest you need to re-examine your understanding of how that Technique operates.
I'm not saying these arguments are perfectly convincing - until it comes up in a saga that I'm in, I really don't care one way or the other. But to state "I can't see any reason" is a sad confession. Maybe "no persuasive reason", maybe nothing that is valid in your opinion - but they are certainly there, your perception not withstanding.
Remember...
"Show me a 'worst case scenario', and I'll show you someone with no imagination."
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