Certain kinds of complex phenomena serve as testing and proving grounds in phonology as theories develop and change. Cases of what I will call CONFLICTING DIRECTIONALITY, exemplified by the stress pattern in Selkup (Ostyak-Samoyed) in (1), constitute one such phenomenon (Halle & Clements 1983, Idsardi 1992). This pattern, first discussed for Eastern Cheremis by Kiparsky (1973) (from Itkonen 1955), has informed all major theories of stress (Hayes 1981, 1995, Prince 1983, Halle & Vergnaud 1987, Kenstowicz 1995, Halle & Idsardi 1995, among others). Descriptively, in Selkup the rightmost heavy (CVV) syllable receives the stress (1a), but if the word contains no heavy syllables, it is the leftmost syllable which is stressed (1b). The term CONFLICTING DIRECTIONALITY describes this elsewhere relationship between the right and left edges of a word. No theory of stress is complete if it cannot account for this pattern.