Below I will first make an inventory of presence technologies that exist today, dd. 2006. Then I will sketch current presence research as it is performed in Europe and the USA, and I will conclude that presence research is a 'science of trade-offs' (IJsselsteijn 2004). Focusing on social interactions to better understand the 'trade-off' I will distinguish between three basic modes of presence: natural, mediated and witnessed presence. I will not use the concepts of social presence and co-presence, which are mainly used in presence research that is concerned with creating Virtual Reality Environments, even though the research carried out in that field will appear to be of great value for this study. Physical presence, co-presence and social presence are used in connection with each other in current presence research to distinguish between the different senses of presences a person can be aware of while being involved in mediated presence, whether this is a book, a video conference or an elaborate virtual environment (IJsselsteijn & Riva 2003).note 20 The question that guides this research is concerned with how mediated and non-mediated presence influence the communication processes of social interaction. I will not distinguish between the variety of senses of presence that can be generated by the different technologies. The effect of mediation itself will be my focus of attention.
Because the presence of other people has a distinct influence on how people orchestrate their own presence - in natural as well as in mediated presence - I introduce the concept of witnessed presence. As I explained in chapter 1, I have chosen The Universal Declaration of Human Rights (UDHR 1948) as the essential normative perspective for the quality of social interaction. In this chapter I will touch upon the UDHR regularly to understand better how presence technologies affect human rights, and thus influence the potential building up or breaking down of trust. In the conclusion to this chapter I will argue that we are dealing with multiple presences in our day-to-day lives and the 'trade-offs' between these multiple presences are the building blocks for social realities.