Are All Creatures Conscious?
Last month I distinguished between the contents and consciousness and the faculty of consciousness. The contents of a dog's consciousness may be different from ours, but it still possesses the faculty of consciousness. (see: The Nature of Consciousness)
A good analogy is that of a painting on a canvas. The possible paintings are limitless, with a great diversity of richness of color and detail, but they all share the fact that they are painted on a plain white canvas. Similarly, the great variety of conscious experiences are all dependent upon the faculty of consciousness.
If mammals such as dogs have the faculty of consciousness, I see no reason to suppose birds don't. Indeed, some parrots I have known seem just as conscious as dogs. What about reptiles and fish? There is nothing particular about their nervous systems to suggest they don't have their own interior world of experience. So where do we draw the line? At vertebrates? Insects have senses and nervous systems; why shouldn't they also have some corresponding degree of inner experience?
It seems probable to me that any organism that is sensitive in some way to its environment has a degree of interior experience. If a bacterium is sensitive to vibration, light or heat, who are we to say it does not have a corresponding degree of consciousness? The picture that is painted might be the equivalent of an extremely faint smudge of colour -- virtually nothing, compared to the richness and detail of human experience, but not completely non-existent.
From this perspective, what has emerged as life has evolved is not the faculty of consciousness but the various qualities and dimensions of conscious experience -- the contents of consciousness. As living beings evolved eyes, ears and other sense organs, the pictures that were painted in consciousness became increasingly richer. To process and use this information nervous systems evolved, and as the nervous systems grew more complex new qualities emerged -- free-will, cognition, intention and attention. With the appearance of human beings, consciousness gained an entirely new dimension -- thinking. It is thinking that sets us apart from all other creatures; not consciousness itself, but the use we make of consciousness.