 A variety of hypotheses have been put forward by scientists and philosophers about which animals are conscious and which are not. These views span a huge range of possibilities, from the narrowest, which is that only humans are conscious, to some authors arguing that almost all animals, even simple invertebrates, have a basic capacity to experience the world. Some authors have even argued that single-celled organisms (Margulis 2001) or plants (A. Nagel 1997) are conscious, and some have given arguments for versions of pan-psychism, the view that consciousness is a property of fundamental physical entities, much in the same way that mass and charge are (Chalmers 2015). It is worth noting that neither the attribution of consciousness to single-celled organisms, nor to fundamental physical entities, implies that all animals are conscious. In the former case, it may be that the information processing complexity and integration of relatively complex single-celled organisms outstrips that of the simplest animals. In the latter case, while the version of panpsychism developed by Chalmers attributes ‘microexperience’ to ‘fundamental physical entities’, this does not imply that any particular macroscopic object (like an animal) has ‘macroexperience’ — i.e. “the sort of conscious experience had by human beings” (Chalmers 2015). This view is compatible with the possibility that a given animal has no conscious experience, although it is composed of microphysical entities which possess conscious microexperience.  These issues will not be discussed further here, as they fall outside the scope of Animal Consciousness. 