It's my understanding that it probably requires training, which is what the guilds are for. Some people can't (one of the Thaumaturge quest lines, for example, has one of the guildmaster's brothers being unable to take up Thaumaturgy because his aether is imbalanced or something, and doing so would likely kill him.)
Most adventurers probably have the potential to learn to use magic, and even though every player character is an "adventurer" they are still a relatively small subset when compared to all of Eorzea. It's up to you to decide what your character can and can't do as far as classes go, or how easily they take to a given school of magic (or not.)
There's potential in RP for not being able to play certain classes because of issues, or having to do so at a certain cost to the character, but you'd have to be careful. Also, the Aetherytes use the Aether to teleport you, but it seems like a relatively commonplace thing that only requires minimal instruction.
Most adventurers probably have the potential to learn to use magic, and even though every player character is an "adventurer" they are still a relatively small subset when compared to all of Eorzea. It's up to you to decide what your character can and can't do as far as classes go, or how easily they take to a given school of magic (or not.)
There's potential in RP for not being able to play certain classes because of issues, or having to do so at a certain cost to the character, but you'd have to be careful. Also, the Aetherytes use the Aether to teleport you, but it seems like a relatively commonplace thing that only requires minimal instruction.
