We take it for granted we live in the three-dimensional space, but we do not perceive the three dimensions directly. Why do we consider the space to be 3D?

You would think you have consciousness, but robots do not. What criteria should we apply for judging whether a certain system has consciousness or not? I would like to suggest a criterion: whether it can waver in its selection or not.

The word system is derived from a Greek word sunistanai (to combine) and a system is usually defined as a group of combined elements. This definition identifies system/element relation with that of whole/part, but a system is not just a whole composed of parts, much less spatial subsumption relation between a whole and parts. What is a system, then?