uebermensch; Unamuno Miguel de; unbounded minimization; unconscious the; uncountable; uncountable set; undecidable set; undecidable system; undecidable wff; underdetermination; understanding; undistributed middle; uniformity of nature; union of sets; universal; universal algebra; universal generalization; universal instantiation; universalisability; universal proposition; universal quantifier; universal set; universals problem of; univocal - equivocal; ursache; urteil; use - mention; utilitarianism; universe of discourse; unmoved mover; upper bound; usability; use theory of meaning; utilitarianism; utility;