Again, Pandora's exact wording "You, You Tedd, will cast it," in the context she's saying it in, that of reassuring Tedd that he never has to worry about losing his cool stuff, strongly indicates that while Seers do not innately have the ability to cast spells that they are capable of gaining the power to do so without having to create an object to cast the spell for them(which is how Wands work--theWand casts the spell either from your energy or the energy in the wand)

Pandora's words, after having exactly what Seers are explained to her, are "You cannot cast spells" and "You will cast it."

These are mutually exclusive statements if you take them as both being absolute, but if you take the first as being present tense and the second as being Future tense...

Again, when Arthur is explaining Wizards to Ashley he states that she will have to Awaken before she casts spells, emphasis mine. If Wizards have to Awaken, and Arthur himself didn't realize he was anything but a wizard, albeit, with a gimmick, we can conclude that Arthur himself has awakened.