Consciousness is notoriously difficult to explain. On one hand, there are facts about conscious experience--the way clarinets sound, the way lemonade tastes--that we know subjectively, from the inside. On the other hand, such facts are not readily accommodated in the objective world described by science. How, after all, could hearing the reediness of clarinets or tasting the tartness of lemonade be described scientifically?

Edmund J. Bourne in his book Global Shift (2008) defines consciousness as a state of being characterized by Sentience, the awareness, both of self and the environment; Subjectivity, the capacity to have a point of view from the inside out; and Self-agency, the ability to be self directed, self organized, capable of choosing freely. Other characteristics include Intentionality, Purpose and Meaning.

In view of these attributes, what is the range of consciousness? Are only humans conscious? How about your pets? My cockatoo certainly seem to be. Does it extend to worms, bacteria? How about trees and algae? If so, in what sense? It seems that living organisms all down the line exhibit at least Self-agency, they all act in their best self interest. The sunflower turns toward the sun, the tree grows its roots for balance on a slope, a bacterium seeks out nutrients. Their experience of consciousness may be very different from ours, but it is certainly in the realm of possibility.

Christian de Quincy in his book Radical Nature (2002) argues that consciousness extends beyond living organisms, not only to rocks and water, but all the way down to molecules, atoms and even subatomic particles. His position is that for a nonmaterial sentient consciousness to appear suddenly out of the material brains of higher order animals and humans would require a miracle. Therefore consciousness must be an inherent aspect of nature all the way down to the smallest particle. If that is true, then even atoms and quarks are capable of experiencing sentience, however dimly reminiscent of the human experience.