The purpose of this paper is to examine a version of externalist epistemology based on the notions of “conclusive reasons” and “decisive indicators”, and to decide whether it is a viable option. There are some good points to be taken from existing criticisms of this position, but my judgment is that they fail to block an extreme externalist reply suggested by Suppe. However, at the same time, I show that almost any pair of experiential state and belief can meet the condition of conclusive reasons (or decisive indicators) using stronger counterexamples. Thus, these notions are nearly trivial, and the version of externalism based on these notions is unattractive.
In Mizumoto & Ishikawa (2002), we introduced a paradigm of experiment which is of interest to both psychology as well as philosophy. This experiment involved a subject wearing a Head-Mount Display (HMD) while a camera was set up in the upper corner of the same room in which the subject was to be found. In the experiment images were sent wirelessly from the camera to the HMD, so that the subject could observe himself from the third-person perspective through the HMD. In this paper we will discuss the interdisciplinary aspect of this experiment, presenting specific results of psychological experiments as examples together with outlines for further experiments.