Articles are inversely associated with inflectional case in Indo-European

Abstract The relationship between inflectional case marking and the emergence of definite and indefinite articles has long been hypothesized but seldom examined quantitatively. This study presents a large-scale statistical analysis of the relationship across ninety-four Indo-European languages. Bayesian logistic regression models account for phylogenetic and spatiotemporal autocorrelation while integrating over phylogenetic uncertainty. The results establish a robust inverse association between case-inventory size and the presence of articles. Estimated probabilities indicate that smaller case inventories are associated with higher probabilities of definite articles. A similar association holds for indefinite articles. The posterior median predicted probability exceeds 0.5 at four cases for definite articles and between three and four cases for indefinite articles. These thresholds correspond to reduced case inventories composed primarily of grammatical cases. Even after accounting for case-inventory size, the presence of a definite article is associated with a higher probability of an indefinite article. The analysis shows that the observed association is compatible with direct, mediated, and common-cause accounts and does not uniquely identify a causal pathway. These findings sharpen the empirical basis of the debate and identify the causal and evolutionary questions that remain open.