I don't think Pathfinder magic is bound into a single language like the true-speak of Earthsea, rather it is a certain mode or manner of speech. Think of a spell like a folk melody with lyrics differing from culture to culture. The individual words don't matter when making a spell craft check, because they each fit into a certain "pattern" which all casters recognize as forming the basis of that spell. A spell may have many different variations, utilizing wildly different gestures and words, but every combination of those words carry's the import of that spell. So, if a human cleric sees an elven priestess cast a healing spell by muttering a prayer in elvish, he can recognize it even though he casts his spells in celestial, because both versions of the spell have the same "rhythm" which he can recognize through his formal training in spellcraft. Following this theory, every tradition of spellcasters would have their own particular method of casting a given spell, bringing about the same results. Bards sing snatches of gnomish ballads which have lyrics fitting the particular "pattern" of a spell, while old elvish wizards chant old elvish litanies, and their human counterparts use ancient draconic formulas. Each variation of a spell might even have subtly different effects depending upon which tradition it comes from. The elvish formula for a fireball spell may create a burst of blue flames, while the most common human variation creates orange and crimson ones, shot through with sparks of gold. A wizard's magic missile may be a neatly formed orb of force, while a sorcerer's might be a sizzling, ragged bolt of energy. These effects allow casters to identify the particular method someone is using to cast a spell, and might produce some snobbery on the part of adherents to individual methodologies. "Ugh, you're using Morgandon's imprecation to the wall of searing flame? Gnomish magic is so common and slap-dash!" This idea also explains how sorcerers can learn the same spells as wizards can without the more erudite mage's reliance on arcane notation. A sorcerer has an innate sense of which sorts of words, gestures, and ingredients form which sorts of spells, and they hone that sense through trial, error, and personal experimentation. Wizards have no need for this instinct because their method of magic use has more or less "cracked the code" on which kinds of components make up which spells. Their notation takes most of the guess work out of spell crafting, getting easily reproducible results. Sorcerers instead use the spark of the natural savant, and thus their spells may have more personal show-effects representing their inner natures. But now I'll stop before I let my pet theories run away with me. :)
