[jbob2000]

I think you're confusing "consciousness" with "cognition". A deer is cognizant; it observes and reacts to the world around it, among other qualities of cognition. But it does not have self awareness and does not have abstract thought or any thought beyond carnal ones (eat, sleep, run, fight, etc.).

Consciousness is definitely measurable and definable, but context is important as the word is used in many different scenarios. Terry Schiavo was conscious (because she is a human and humans are conscious beings) but was also not conscious (because she lost her faculties for consciousness).

To your points, the first step of talking about consciousness is defining the "rules of engagement", the context under which consciousness is discussed. Practically speaking, consciousness is a trait that separates humans from "everything else". When things display human-like tendencies (reacting to pain, showing affection, communicating, using tools, etc.), we say they are "conscious".