Normally, gestures and words are needed to cast a spell. It is usually possible to eliminate this requirement by raising the Difficulty by 2 to eliminate either words or gestures, or by 5 to eliminate both. Spells close to the caster's limits, however, require some aid in casting by using hand and body motions or chanting. Any time the Complexity of the spell is greater than the caster's (Skill Rank + Magery) x 2, an incantation is required. Gestures are required for any spell which is ``directed,'' such as an attack spell, or any time the Scope of the spell is greater than the caster's Willpower plus Spirit.
Example: An Elementalist casts the sample ``Flame Blade'' spell. His Intelligence, Mind, and Willpower are all 3, his Spirit is 2, his Magery is 3, and Skill in Fire Path is 5. He casts from a Matrix, and rolls an 8, for a total of 19. The Difficulty is 13, resulting in an MoS of 6, which reduces the Backlash from 11 to 5. When casting, he does not require an incantation(Complexity 14 is 
(Skill 5 + Magery 3) x 2 = 16), but he does require gestures to complete the Spell(Scope 6 is 
Willpower plus Spirit of 5).