Consciousness is what makes us what we are; however it is very difficult to examine our internal workings and form an external definition for something everyone uses everyday. This is mainly because the mechanisms of consciousness are still a mystery.
Here are two well accepted definitions.
Consciousness is the quality or state of being aware of an external object or something within oneself. It has been defined as: sentience, awareness, subjectivity, the ability to experience or to feel, wakefulness, having a sense of selfhood, and the executive control system of the mind. Despite the difficulty in definition, many philosophers believe that there is a broadly shared underlying intuition about what consciousness is. As Max Velmans and Susan Schneider wrote in The Blackwell Companion to Consciousness: "Anything that we are aware of at a given moment forms part of our consciousness, making conscious experience at once the most familiar and most mysterious aspect of our lives."
Philosophers since the time of Descartes and Locke have struggled to comprehend the nature of consciousness and pin down its essential properties. Issues of concern in the philosophy of consciousness include whether the concept is fundamentally valid; whether consciousness can ever be explained mechanistically; whether non-human consciousness exists and if so how it can be recognized; how consciousness relates to language; whether consciousness can be understood in a way that does not require a dualistic distinction between mental and physical states or properties; and whether it may ever be possible for computing machines like computers or robots to be conscious.
-wikipedia
In 1994 David Chalmers published a paper explaining why consciousness is such a challenging phenomenon to understand. Although he wasn’t the first to discuss these challenges, he was the first to categorize them into two types of problems: “easy” problems and the “hard” problem. Easy problems involve the explanation of how the mind integrates information, focuses attention and allows us to report on mental states. Though not a piece of cake, such problems are easy because solving them only requires that we determine the mechanisms that explain these behaviors. Easy problems are physical by nature, falling within the empirical domains of psychology, cognitive science and neuroscience. Given the current trend in science of the mind, we’re confident that one day we will solve these problems.
The hard problem, by contrast, may never be solved. Specifically, the hard problem is determining why or how consciousness occurs given the right arrangement of brain matter. What makes it hard is that we cannot just point to some physical mechanism to solve it, for that would be the solution to the easy problem. Instead, our goal is to explain why certain physical mechanism gives rise to consciousness instead of something else or nothing at all. Consider an analogy from physics: knowing every equation predicting how mass and gravity interact does not tell us why they interact in the way they do. To understand why mass and gravity interact, we must appeal to highly esoteric explanations involving relativity, quantum mechanics or string theory.
-What is Consciousness?
