Article Brey, P. (2005). The epistemology and ontology of human-computer interaction. Minds and Machines,15(3-4), 383–398. Epistemic functions are what have traditionally been called information processing functions. In an epistemic function, the computer functions as a cognitive device that extends or supplements human cognitive functioning by performing information processing tasks. As long as they have existed, computers have functioned as cognitive devices, or cognitive artifacts, and this epistemic function remains important in contemporary computers. I will argue, however, that in recent decades, the computer has acquired a new class of functions, which I term ontic. In their ontic role, computers simulate environments and tools to engage these environments. I will argue that this ontic function is not properly understood as an information function, even though it is dependent on the information processing capabilities of computers. I will be arguing that the computer is a special kind of cognitive artifact that is capable of extending a broad range of cognitive abilities of human beings. Cognitive artifacts are properly called cognitive’ because they, in quite straightforward ways, extend human cognition. They help us think, plan, solve, calculate, measure, know, categorize, identify, or remember. Various classes of cognitive artifacts may be distinguished, based on the primary cognitive capacity or capacities that they extend or aid. The functional analysis of computer systems presented here has identified computer systems as both cognitive devices and simulation devices. As a cognitive device - the computer extends human cognintive faculties by both supplementing and enhancing them. As a simulation device, the computer does not so much extend human faculties as extend the world. Computer generated, virtual environments, and Internet-generated social structures offer extensions of "real" world that are useful and important for entertainment, creative activity, learning, and social interaction.