Without an absolute reference to standards of space and time the outcome of such an event cannot be specified. The reference required is that which has already been given, i.e. unit space coupled with unit time. The previous discussion of an absolute standard reference cannot be completely correct, for to exist relative to something is to interact with it. To interact with means to change state. There are then two contradictory requirements to existence.
Interaction is the embodiment of logical operations.
Therefore, just as any abstract unit is embodied in some form, the fact of its existence relative to other units is embodied in the manner of an interaction, i.e. causal change in the form of the unit or in its relationship to other forms. Thus, a 'ghost' passing through other forms without the capacity to influence them is simply a variant non-existent. To exist is to interact with others. A brief definition of existence is 'consistency of interaction'. To understand this and its ramifications observe the following thought experiment.