According to Paul Ernest (1991) 'philosophical schools of thought have a direct bearing on educational issues'. More specifically, a researcher's influences on her approach to mathematics education research include her perspective on mathematical learning, namely on their beliefs on how mathematical knowledge grows as a discipline as well as within the individual learner. Here I present the views espoused in this study about the phylogenetic (mathematics as a discipline) as well as the ontogenetic (mathematics as learned by an individual, cognizing subject) growth of mathematical knowledge. Subsequently a resulting philosophy and psychology (Part II) of mathematics education is presented. I note that the purpose of this presentation is to highlight the philosophical views that relate to the formation of the theoretical underpinnings of the study: therefore it is concise and does not have the structure — or the aspirations — of a philosophical debate.