Kai Frederick Wehmeier (born 1968) is a German-American philosopher and logician.

He is best known for proving that the fragment of Frege's inconsistent logical theory of Grundgesetze der Arithmetik becomes consistent upon restricting the complexity of comprehension formulas in the second-order comprehension schema to ${\displaystyle \Delta _{1}^{1}}$, for his development of a system of subjunctive modal logic and its use in rebutting Kripke's modal argument against description theories of proper names, as well as for refining and defending the thesis that there is no binary identity relation between objects.

Wehmeier is currently a professor in the Department of Logic and Philosophy of Science and the Department of Philosophy at the University of California, Irvine. He is also the director of UC Irvine's Center for the Advancement of Logic, its Philosophy, History, and Applications (C-ALPHA).^[2]

• "Consistent Fragments of Grundgesetze and the Existence of Non-Logical Objects," Synthese 121, 1999, pp. 309–328.
• "In the Mood," Journal of Philosophical Logic 33, 2004, pp. 607–630.
• "How to live without identity—and why," Australasian Journal of Philosophy 90, 2012, pp. 761–777.
• "Subjunctivity and Conditionals," The Journal of Philosophy 110, 2013, pp. 117–142.

• Wehmeier's personal website
• Center for the Advancement of Logic, its Philosophy, History, and Applications (C-ALPHA)