Minor Supernatural Virtue: Greater Magical Defenses
The wizard is unusually difficult to
affect with magic; double his Magical
Defense Bonuses. This is only useful for
a wizard whose tradition includes Magi-
cal Defenses. If the wizard acquires
a Magic Resistance (he learns Parma
Magica, for example) it is not affected
by this Virtue.
Could a Hermetic magus take this to double their form bonuses?
Not with this virtue, IMHO.
Hermetic defenses are already much better than those of other magical traditions.
Magical Defense Bonus is a term of art used in Hedge Magic Revised. It is not quite the same as a Form Bonus. It is, however, calculated the same way (for hedge Arts) as the Form Bonus is. And if a Hermetic wizard wanted to double their Form Bonus (but not for the purpose of Magic Resistance), that would probably be about the equivalent of a Minor Virtue. So...
RAW no- it was either rival magic or hedge magic iirc that went out of its way to say hermetics can't take the virtue. And besides, Form bonuses aren't magical defenses.
That being said. There's no reason this couldn't be a project for integration by a hermetic researcher.
Perhaps you are choosing the phrase to have a very narrow, technical meaning within the RAW. But I don't know what it is at this time.
If you have a high Ignem score, you are able to Soak more damage from Fire, natural or magical. Likewise a high Terram score allows the mage to Soak more damage when poked by sharp metal weapons.
Would this not be "magical defense"?
Not in the sense of Magical Defenses as defined in HM:RE or Rival Magic, and that is the only type that the virtue Greater Magical Defenses or the flaw No Magical Defenses (from the same books) apply to.
No- it isn't.
If you look at hedgirs, their magical defenses is rather specific- stuff like being able to accelerate the duration of spells or roll to resist. It often doesn't actually directly relate to the Form referenced, except to limit the scope.
The main exception are the sahirs- I could see a valid argument that they aren't applicable for Greater Magical Defenses since it is compared to Form bonuses. There's a good chance the only reason it isn't called Form bonus imo is because sahirs don't use the Form+Technique style.
Either way- Magical Defenses is a mechanically defined thing that I don't believe hermetics are applicable for or intended to be applicable for.
One of the options for hedge Magical Defenses gives a Soak bonus (Magical Fortitude), just like Hermetic Form Bonuses do. Each hedge Ability or Art may give a type of Magical Defense against a category of effects, like Corpus effects or Mentem effects... just like Hermetic Form Bonuses do.
Hermetic Form Bonuses give a few extra benefits here and there in addition to Soak bonuses, but trying to argue that they're dissimilar is silly.
Of course they are similar. Nobody has argued otherwise.
That doesn't make them the same though.