Arcane Thesis( Player's Handbook II, p. 74)
You have studied a single spell in-depth. Your expertise grants you formidable though narrowly focused arcane mastery.
Knowledge (arcana) 9 ranks, ability to cast arcane spells,
Choose one arcane spell that you can cast to be your thesis spell. When casting that spell, you do so at +2 caster level. When you apply any metamagic feats other than Heighten Spell to that spell, the enhanced spell uses up a spell slot one level lower than normal. Thus if you were to prepare an empowered maximized magic missile (assuming magic missile is the spell you choose for your Arcane Thesis), it would be prepared as a 4th level spell (+1 level for empowered, down from +2; and +2 levels for maximized, down from +3).
A spell cannot be reduced to below its original level with the use of this feat.
You can gain this feat multiple times. Its effects do not stack. Each time you take the feat, it applies to a new spell.