You appeal to sound reasoning and fact, rather than to emotion, when attempting to sway others.
If you have at least 10 ranks in Diplomacy and an Intelligence score of 27 or more, this bonus increases to +8. This bonus doesn’t stack with the bonus from Skill Focus (Diplomacy), but this feat counts as Skill Focus (Diplomacy) for the purpose of feats and other elements with Skill Focus (Diplomacy) as a prerequisite. In verbal duels, when using tactics to which you assigned an Intelligence-based skill, you can add your Intelligence modifier instead of your Charisma modifier to the associated skill check.
Pathfinder Roleplaying Game Ultimate Intrigue © 2016, Paizo Inc.; Authors: Jesse Benner, John Bennett, Logan Bonner, Robert Brookes, Jason Bulmahn, Ross Byers, Robert N. Emerson, Amanda Hamon Kunz, Steven Helt, Thurston Hillman, Tim Hitchcock, Mikko Kallio, Rob McCreary, Jason Nelson, Tom Phillips, Stephen Radney-MacFarland, Thomas M. Reid, Alexander Riggs, David N. Ross, David Schwartz, Mark Seifter, Linda Zayas-Palmer.