THE DISTRIBUTION OF CONSCIOUSNESS

Are we the only conscious beings? We know that we are conscious, but what is the wider distribution of consciousness? How did consciousness evolve? And what kind of universe could have produced it? Dualists and reductionists alike have expressed many different views on these matters. As all the data needed to decide these matters are not currently available, all views are partly speculative.

Why are all views about the distribution of consciousness on our own planet or in the wider universe partly speculative? Because we do not even know the necessary and sufficient conditions for consciousness in our own brains! As E. R. John (1976) pointed out, we do not know the physical and chemical interactions involved, how big a neuronal system must be to sustain it, nor even whether it is confined to brains – and over thirty years later we are little wiser (see the review of the neurophysiological evidence in Velmans 2009, chapter Given this under-determination by the data, opinions about the distribution of consciousness have ranged from the ultra-conservative (only humans are conscious) to the extravagantly libertarian (everything that might possibly be construed as having consciousness does have consciousness).

The view that only humans have consciousness has a long history in theology, following naturally from the doctrine that only human beings have souls. Some philosophers and scientists have elaborated this doctrine into a philosophical position. According to Descartes only humans combine res cogitans (the thinking stuff of consciousness) with res extensa (extended material stuff).