Are you conscious? If you're reading this, I will assume you are. However, in the near future, we may well have robots that can read, speak, and answer an assortment of questions put to them. If that becomes a reality, would we be willing to accept the notion that such robots are also conscious? Obviously, this all depends on our definition of consciousness. And, surprisingly, we don't yet have a universally agreed upon test for, or definition of, consciousness. Nor do we know what the minimal requirements are for an organism to be conscious. Is it sufficient to possess a complex and functioning brain?
In medical practice we say someone is conscious if he or she is capable of responding to our questions, reacting to painful stimuli, and demonstrating they are oriented with respect to time, place and person. But we know that certain diseases or injuries affecting the brain can seriously impair a person's ability to respond to these tests without causing any significant impairment of their consciousness. For example, most patients afflicted with the "Locked-in Syndrome" can at least move or blink their eyes and thus can be taught a code with which to signal their answers to questions pertinent to their state of consciousness. Without this ability to communicate in some fashion we would have no way to tell whether or not such patients were conscious. The situation is further complicated by the phenomenon of sleepwalking. In this dissociative state humans can carry out complex purposeful actions, like driving a car, but won't remember what they did or why they did it when they come out of this state. Are sleepwalkers therefore unconscious while in a dissociated state?
The dictionary emphasizes being aware and having the ability to think as defining consciousness. But all living organisms respond to at least some external stimuli and are thus aware. So how can we tell if someone or some other organism is thinking if we can't communicate with them? Does your pet think? And what is thinking anyway? Is it merely the ability to communicate with oneself silently? Hopefully, further research on living brains will help us answer some of these questions.