I know that page 149 of ArM 5 suggests you need someone to read writing to be able to then translate it by reading their mind: however is there any alternative in 5th edition canon? By that I mean, magical translation of an unlearnt language. I cannot find one and wonder whether it should be impossible.
Well if you are talking about thoughts rather than written words then you can apply mentem magic to the thinker to translate. Such as thoughts within babel.
Hermetic magic doesn't have a way to grab a hold of the meaning within a text. It can use imagonem to mess with the text but the meaning resides within minds that interpret a text not within symbols themselves.
If you want to modify this for your own game keep a sharp eye on the game breaky-ness of the subject. Look for ramifications with any spell guidelines that you create with a mind to speed reading and instant writing.
Hi Cornelius 
In continuation of Erik's fine points I'll take the liberty of tossing in a few thoughts I had about the same subject in another earlier thread.
Having said that I think it should be quite easy to simply toss away the worries and allow it. It would even have a mythical ring to it; might even be a great cause for a Breakthrough (imagine the lost knowledge to be unlocked!!!). This becomes even more true if you were to use the Adamite Language from Ancient Magic.
Ooh, this brings up a good idea. Could you learn a language from an unwilling teacher entirely by using InMe? Just "read" the language out of their head? I wonder how to figure the source quality of such a method.
Wouldn't a person be like a summa on their native language with a level equal to their native language level?
I am not suggesting an instant gain of experience, but rather an alternative to texts.
You could use this to learn a language from someone who did not share a common tongue with you, and in an area where you were not surrounded by a foreign language (re: practice rules), and without a physical text. Perhaps this could be an interesting way to learn Adamic.
SP, but to learn Adamic the slow safe way would require, for example:
Latin 5 + Greek 5 + European Lore 5 => Cainite 5
Hebrew 5 + Aramaic 5 + Middle East Lore (Holy Land Lore) 5 => Semitic 5
Cainite 5 + Semitic 5 + Babylon Lore 5 => Adamic 5
750 Exp and a whole lot of seasons of work. Wow.
Assuming the magus starts with the first two at 5, and European Lore at 3, that would take (SP) 285 seasons, or 71 years +. Wow!
If you can obtain a means to summon a spirit or ghost the understand the language, and control or bargain with it, you could have it translate the text for you. I believe several demons and angels are said to be capable of reading and speaking any language.
While you're at it, I believe several demons and pagan deities have been acredited with knowledge of magic - so summon Hermes and make him teach you. 
Better measure anything a demon translates verrry carefully, though.
I believe the meta-design of 5e is that the magus should get off his but and go find learn the language or find a speaker : it is too much of an adventure-shortcut to have a "translate the plot maguffin"
Only this week something similar arose IMS. One of the magi suggested crafting an earring enchanted with a thoughts within Babble spell. The moment some foreign type started yammering at him in an unknown language, he'd simply stroke his earlobe and behold! translation.
Am i to understand that this would not work? I always thought Thoughts within Babble allowed to you understand any speech. Is it in fact mind reading? And if it is that would surely mean that parma/MR would block it from working.
TWaB is mind reading, yes. It would be resisted by MR. So it would work, or at least could work just like reading the mind of someone reading in a foreign language could be used to translate the language.
Of course it won't translate the wizard's words back to the person. (Peraps that's a MuMe spell?)
Another option would be to cast an InMe spell with T:Hearing, allowing you to basically understand anyone's speech. (But again, not to answer back, and you still need to penetrate MR.)
This highlights what for me is one of the fundamental weaknesses in Hermetic Magic as of 1220 - it's lack of objective divination. Ironically, given that divination in other game systems is often seen as a fairly basic form of magic, hermetic magic really struggles with it. This is great from a gaming point of view, as it allows GMs to play with wildly powerful magi without the fear of plot circumvention. It is also very neatly and consistently explained through the hermetic laws.
However, if hermetic magic could find a way to discover Truth and then directly influence this they would be able to achieve a huge number of effects. You would no longer require on subjective truth a la Mentem to detect lies (foiled if someone believes they are telling the truth), making intellego far more potent - no more problems detecting Bjornaer heartbeast, if you are able to divine the truth of being. Muto Truth would be a far more effective form of teleportation - no movement is involved, you just change an objects objective position from XYZ to ABC. Creo and Perdo Truth if even possible would lead to reality-changing effects.
It strikes me that you wanted to sum up the divine in a hermetic context, or consider what might happen if magic rather than working on platonic shadows directly influenced Ideals, this could well be it.
Not stricly on topic but this thread has inspired tow thoughts for mentem magics
Tounge of the Xenophile
Mu Me ?
Range Personal Duration Diameter Target individual
The caster's mind is altered for the duration of the spell so that the caster's understanding of a particular language is replaced by the understanding of a language known and spoken by someone else within voice range. For instance a magus who does not understand Bretton could cast this spell while within voice range of a bretton speaker and transform his own understanding of Icelandic into the bretton speaker's understanding of Bretton. This spell needs to penetrate any magic resistance that the "language supplier" has in order to function.
(no guidelines here to compute spell level with)
The second spell is peering into the mortal mind but with a duration of moon instead of instant (does that make it level 45?). The caster then uses the mond that he's peering into as a source of study. My first thought along these lines is to have the spell provide experience as if the caster were being trained by the target, this means that the more a character knws the better the caster can learn and it also means that arts can not be taught.
Thanks to everyone. I had seen the earlier thread. I was wanting to be absolutely sure no one was going to comeup with a rule that contradicted what I suspected. I might suggest it would be a major breakthrough!
I think that allowing the magic to decipher text puts too much sentience into Hermetic magic. One of the defining aspects of Hermetic magic is that, theurgy aside, it is an expression of the magus' will through the Gift.
To give spells the ability to translate text from languages the magus doesn't know into ones the magus does know implies an intelligence acting behind the spell with knowledge that the magus lacks-- and that's drifting into the sort of spells that (should be?) are more Infernal or Divine....(maybe, in some cases, Faerie, depending on your basis for the Fae) in my opinion.
Divination is a whole other kettle of fish-- I think cryptic clues to a text that might assist in translation could be gleaned from proper divination of a text, but straight Hermetic formulaic spells that insert (unspoken, unknown) greek text here and spit out (fully formed and translated) latin text there are right out sans an intelligent middleman (creature?).
-Ben.
I concur! And it would hollow out the essence that makes certain Infernal, Divine and Faerie aspects mythic. The Enigma would also loose some of its lure. But most importantly it would make a long range of interesting stories impossible to tell.
If translation spells were easy to get my whole saga would break away. ^^
Even magi must have some weakness, otherwise a game would boring.
I OTOH have always played that thoughts within bable allows you to talk a language as if you had a level 3 in it. It has not supposed a problem here, since the magus casting the spell has a rough understanding of the meaning of stuff, but his companions do not. It is still a tricky proposition.
I guess it is an issue of "whatever works in your saga" 
Cheers,
Xavi
Talking is one thing - but reading a completely other! When talking you'd presume that you're talking to someone - then using Mentem to talk is not a problem. But if reading, no other mind is present and that's where you got the kabaaang...
True. It has never been a relevant plot device IMS, though. Thinking in retrospective, it could have been in past sagas, but we did not use it. I would prefer to rule out auto-translation of texts, but not ogf words. In a sense, i guess I would allow literal transalation (grammar-less translation) as if the PCs had a handy magical Latin dictionary. Can make for some quite garbled up texts out there 
Enough to get the general meaning, but worthless for deciphering the details or study. And it takes time: something most PCs do not have in a gaming session....
Best,
Xavi