Consciousness
There is no consensus on consciousness! No definition is accurate enough, no description is complete, and no explanation is satisfactory. Yet it is the means with which we discern reality, comprehend our environment, and experience what we are feeling.
Artificial Intelligence
Thanks to Artificial Intelligence, there is a renewed interest in Consciousness not only among those computer scientists who are trying to replicate neuronal networks (and calling them neural networks) but also among neuroscientists, psychologists, and philosophers who have always had a problem with the duality of mind and body. Neuroscience continues with the study of brain structures and perception while psychologists study behavior and behavioral changes brought about by mild or major trauma.
Consciousness cannot be defined or described - rather its descriptions appear to include everything... and then some more. It expands to consume everything so one can't try to isolate it by saying, "This is not consciousness." Because, the minute you say it, consciousness make it a part of itself. Did you know: The Hubble Telescope's Deep View of the Universe Is Now Even More Astounding!? If you didn't, then the minute the question was asked you got to know about it. Your consciousness made it a part of itself.
Tantra does not define consciousness, it expands it - even making us realize deep space!
Self-Consciousness
However, there are aspects of consciousness that can be ascertained, such as self-consciousness. This is different from self-awareness but if that isn't obvious then - for now - let's assume both mean one and the same. Unless there is a major mental handicap or trauma to the brain, we are all self-aware or have self-consciousness: I know who I am!
Do dogs and cats have self-consciousness? Perhaps they do! But does a bacterium have self-awareness? There is no brain so there are no complex brain processes to create anything akin to the human mind. They may not be self-conscious, but they do go against the physical law of Entropy by consuming and reproducing (replicating) so we know they are alive, and by that logic, they are conscious through some definition of consciousness.
Total Recall
Memory serves as a mechanism to remind us who we are and that is an attribute of being self-conscious. But the mechanism of memory is not perfect. If all information is stored perfectly (we don't know if that is the case), then recall of that memory is not at all efficient - a computer does a better job of memory recall. In Kundalini Tantra practice, practitioners often recall memories from many years ago and memories that they are surprised were even stored. Tantra Yoga also evokes sensations from the past and many of these can be quite vivid. While psychologists and philosophers are amazed at our awareness of self-awareness (conscious of being conscious) Tantra manages to ensure being aware of being in a dream. Tantriks often control their dreams and can thus conjure up exciting dream escapades. Being "awake" in a dream is nothing new but Tantra helps you to control it.
There are many pathological states of the brain that tell us of the different manifestations of consciousness: from coma and vegetative states to selective mutism and brain death. If a brain dead person is still not considered dead - and can be kept alive through machines - then can we say there is no consciousness? What about the times when a person is insane (you can use whatever medical term for insane) or when the person is high on drugs or alcohol?!
I Am That!
In Tantra, every factor of reality is endowed with consciousness because of its inseparability with intelligence. The subjective nature of reality is seen to be more logical and provide a better rational picture than objectivity. Consider the following example: You're driving and see a complete stranger. Before that moment, the stranger didn't exist and after you have lost sight of him/her, you don't know if he/she continues to exist. Objectively speaking, you can't be sure whether the person continues to exist and you will have to conclude that you don't know. But the mind can't accept a vacuum so it rationalizes!
Tantra says that the world is created by you and it is the way you see it - not only the way you see it but the way you want to see it. If you're feeling great, then a bleak, rainy day becomes an excuse for cuddling up with some coffee and a good book, but if you're in pain, the the same day will only add to your depression!
There are stimuli in our environment that cause changes in neurons and these changes can be detected by machines. Tantra has documented this over hundreds of years! A great example is how blind people "sense" their stimuli. You don't have to be blind to understand this: simply think of all the times you walk up or down some stairs and you will realize that your body (your feet) are automatically adjusting. You trip only once in a while.
There is mind-body dualism but there is also the dualism of conscious mind and unconscious mind. We can go on about dualities and pluralities: sub-conscious and conscious perception, verbal and nonverbal communication, objective and subjective experience, and so on.
The Mind
Whatever consciousness means, tantric texts and traditions are concerned mainly with the expansion of consciousness. While the modern-day Science of Consciousness explores the meaning and mechanism of the mind, Tantra offers techniques to expand our mental faculties. We popularly agree that consciousness emanates from the mind and that it is a manifestation in higher-order animals. But closer examination will show that we are conscious of the "concept of mind." In other words, our consciousness makes us 'realize' the mind. The logical exploration of the cause of our consciousness leads us to create a mind. Therefore, consciousness is not a manifestation of the mind but the other way around: The mind is a fabrication of our consciousness!
Expansion of Consciousness and Tantra
Our popular understanding of consciousness and even awareness is basically wakeful awareness and our understanding of the physical world. Since we are part of the physical world, we are part of reality. Serious exploration of this wakeful state will show that there are many different forms of this type of awareness, but we won't get into that. We live our life based on our thoughts that emanate during this state of awareness. But, thanks to Sigmund Freud, we know that those thoughts have their origins in other states of consciousness: what we broadly categorize as either the subconscious or the unconscious!
Based on what we call consciousness, our notions of reality may also change. How real is a vivid dream or nightmare? How real is a hero or villain in a movie? How real is our experience of joy or pain? By making awareness a part of any instance of Reality, Tantra makes all of Reality a part of consciousness. Therefore, our different experiences of different events of reality are categorized in different tattvas.
Who am I?
A person can be in a state of self-awareness and not be aware of it. Example: When we wake up from being asleep, we may ask ourselves, "Where am I?" but never, "Who am I?" (Unless you're Jason Bourne!) However, any person who knows what they are doing or who has some awareness of their actions will always know when something is wrong. That is the definition of consciousness. When Tantra talks of focusing on the present and concentrating fully on the task at hand, then we are "conscious of being conscious;" at any second, I am aware that, "I am doing what I'm doing."
People have a wide range of emotions and states of consciousness - it is impossible to capture everything that is going on in someone's mind. This is why scientists attempt to use machines that can simulate these states. However, these machines cannot fully emulate the more advanced forms of consciousness.
Artificial Intelligence therefore cannot become self-aware till it reaches a state of complexity that is at least as complex as a creature's brain. A computer program can capture a small part of the information and not the meaning behind that information.