Masaharu Mizumoto

This work explores the conceptual and empirical issues of the concept of knowledge and its relation to the pattern of our belief change, from formal and experimental perspectives. Part I gives an analysis of knowledge (called Sustainability) that is formally represented and naturalistically plausible at the same time, which is claimed to be a synthesized view of knowledge, covering not only empirical knowledge, but also knowledge of future, practical knowledge, mathematical knowledge, knowledge of general facts. Part II tries to formalize the natural pattern of belief change assumed in Sustainability in terms of a specific formal theory of belief change, after carefully examining the notions of belief, belief change, and Information, from which the cognitive function F in Chapter 3 is actually constructed, which is later implemented by a computer program and its behavior against random input is demonstrated. In Part III we proceed to examine the analysis empirically. In particular, we will investigate Sustainability from the developmental point of view. We first justify experimental approach in philosophy as a legitimate method of philosophical investigation, and then developmental approach in particular. The specific proposal of experiment here is what we call the Gettier Task, an analogue of the famous false-belief task in developmental psychology, which has been much discussed in philosophy of mind. Two versions of the Gettier Task were tested on children aged from 6 to 12, and we claim that the data obtained empirically supports our analysis of knowledge, or Sustainability.