The Linguistic Architecture of Mathematical Thought (Part 1): Why Do Toddlers Use the Past Tense in Make-Believe Play? A Third Answer to the Counterfactual Past and the Marker of 100% Settledness

Across the globe, three to four-year-old toddlers spontaneously deploy past tense morphology when initiating pretend play (the ludic past), despite lacking the capacity for complex logical computation. This phenomenon mirrors the use of the "fake past" in adult counterfactuals, presenting a long-standing puzzle in theoretical linguistics. Challenging both the modality/exclusionary approach (Iatridou 2000) and the temporal shift approach (Ippolito 2013), this paper proposes a third, cognitively grounded framework: the past tense functions fundamentally as a marker of 100% settledness. Drawing on comparative data from Japanese (the perfective auxiliary -ta), Mandarin Chinese (the aspectual le), and Indo-European languages, I propose that because verbs inherently encode uncertainty, interlocutors appear to recruit past/perfective morphology to artificially freeze the premise into an unmovable cognitive scaffold. This paper establishes the foundations of this hypothesis, paving the way for a broader evolutionary inquiry into verb primacy, metabolic nominalization, and horizontal linguistic transfer.