Champions of deductive reasoning and logical insight, empiricists put their faith in facts, data, confirmed observations, and consistently repeatable experiments—these things are their currency of truth.
An empiricist's ability to notice the minutiae of almost everything that happens around him allows him to make shrewd and insightful calculations about people and even inanimate objects. At 2nd level, an empiricist uses his Intelligence modifier instead of the skill's normal key ability for all Disable Device, Perception, Sense Motive, and Use Magic Device checks. He can also use his Intelligence modifier instead of Charisma on any Diplomacy checks made to gather information. This ability replaces poison lore and poison resistance.
An empiricist's grasp of facts and data enables him to anchor himself in reality, granting resistance to even the most potent illusions. At 4th level, an empiricist gains a +2 insight bonus on all Will saving throws against illusion spells or spell-like abilities that allow a save to disbelieve their effects. In addition, he can expend one use of inspiration as an immediate action to use his Intelligence bonus instead of his Wisdom bonus on all such saves for 1 round.
At 8th level, the empiricist's insight bonus increases to +4. At 16th level, he gains immunity to all illusion spells and spell-like abilities that allow a save to disbelieve their effects. This ability replaces swift alchemy.
An empiricist's powers of reason and deduction ultimately become almost superhuman, and he is able to use them in nearly all aspects of life. At 20th level, an empiricist can use inspiration on all skill checks (even for skills he is not trained in) and all ability checks (including initiative checks) without spending uses of inspiration. This ability replaces true inspiration.