Consider this propositional function which includes the dyadic predicate “loves”: “X does not love Y unless Y loves X” (or “if Y does not love X”). This function may be treated in four ways. (1) If universally quantified, it states a (purported) conceptual truth about “love” or the nature or essence of love. Love is necessarily reciprocal. (2) If universally quantified, it may alternatively be a nomological generalization stating an empirical or factual truth about human nature, i.e., about a pattern (...) of reciprocity that occurs among people who are independently identified as lovers. (3) If instantiated with constants, it is an empirical proposition about the attitudes or behaviors of particular individuals (a, b, c). Finally, (4) the function may be treated axiologically; it expresses a normative judgment about what love ought to be or what lovers ought to feel or do. Other propositional functions may be constructed for the constancy, exclusivity, and benevolence of love. This essay investigates the implications of these understandings of the function and how they are logically related to each other. (shrink)