This essay prescribes some broad ‘Cartesian‐Uniformitarian’ boundary conditions for linguistic hypotheses about Creole formation. These conditions make constructive connections between Creole studies, historical linguistics and language‐acquisition research. Here ‘Cartesian’ has a mentalist sense, as in Chomsky (1966): I consider the formation of so‐called ‘Creole’ languages to be ultimately reducible to the creation, in certain sociohistorical contexts, of certain idiolects (i.e., individual internal, or ‘I‐’, languages) in the minds of the ‘first “Creole” speakers’. To avoid circularity, my use of the term ‘Creole’ in the phrase ‘first “Creole” speakers’ combines some of its original ethno‐historical senses: I use the word ‘Creole’, in this particular context, to refer to the non‐indigenous people of African or European descent that were born and raised in the colonial New World, in opposition to those that were born and raised in the Old Worlds of Africa and Europe. The term ‘Uniformitarian’ evokes Neogrammarian approaches to language change, as advocated, for example, by Osthoff and Brugmann (1878) and Paul (1890). It summarizes my fundamental working assumption that no sui generis or exceptional linguistic processes need to be postulated in order to explain the creation of these languages that have come to be labeled ‘Creole’: these languages were created by the same psycholinguistic mechanisms that are responsible for the creation of (I‐)languages, and for linguistic diachronic patterns, everywhere else. Therefore, ‘Creole’ languages cannot be distinguished a priori from non‐‘Creole’ languages on any linguistic‐theoretical criteria – and ‘Creole’ languages can be genetically classified by the Comparative Method, on a par with non‐‘Creole’ languages. Such assumptions go against popular claims about Creole genesis such as those in, for example, Thomason and Kaufman (1988), Lefebvre (1998) and Bickerton (1999). In establishing these Cartesian‐Uniformitarian guidelines, I correct category mistakes that fail to distinguish explanations that apply to I‐languages from explanations that apply to E(xternal)‐languages and other social‐group phenomena that I‐languages are implicated in. One such category mistake concerns the ontology and time course of innovations in specific I‐languages vs. their spread across populations of I‐languages and into E‐language communal norms. Then I investigate the possible – and impossible – contributions of first‐language acquisition and second‐language acquisition to ‘creolization’. In particular, I take my cues from: (i) studies of language‐ and dialect‐contact situations where children and adults seem to play observably distinct roles; and (ii) recent discoveries about instances of Sign Language acquisition and creation where the Primary Linguistic Data seem remarkably restricted. As for elucidating the limits on the restructuring capacities of children and adults, and their respective contributions to language creation and change, it is epistemologically safer to investigate instances of diachronic development that are more recent than the now unobservable early stages of ‘creolization’. Throughout this essay, I use the term ‘creolization’ strictly as an a‐theoretical abbreviation for the longer phrase ‘development of these languages that, for sociohistorical reasons, have been labeled “Creole” ’. In the perspective sketched here, creolization is just another instance of language change – or ‘language evolution’, in Mufwene's (2001, 2008) sense – the investigation of which is to shed light on Universal Grammar.