Consciousness, at its simplest, is awareness of a state or object either internal to oneself or in one's external environment. However, its nature has led to millennia of analyses, explanations, and debate among philosophers, scientists, and theologians. Opinions differ about what exactly needs to be studied or even considered consciousness. In some explanations, it is synonymous with the mind, and at other times, an aspect of it. In the past, it was one's "inner life", the world of introspection, of private thought, imagination, and volition. Today, it often includes any kind of cognition, experience, feeling, or perception. It may be awareness, awareness of awareness, metacognition, or self-awareness, either continuously changing or not. The disparate range of research, notions, and speculations raises a curiosity about whether the right questions are being asked. Examples of the range of descriptions, definitions or explanations are: ordered distinction between self and environment, simple wakefulness, one's sense of selfhood or soul explored by "looking within"; being a metaphorical "stream" of contents, or being a mental state, mental event, or mental process of the brain. Source: Wikipedia (en)