Pain has not to be considered a false step of nature. On the contrary, it is an extremely effective warning mechanism through which the individual becomes aware of a danger to its own physical integrity from inside the body or from the environment. Pain therefore belongs to the biological devices for evading bodily danger. The conscious experience of pain is the most sophisticated stage of evolution of warning systems, whose simplest form is represented by an unicellular organism which moves away if it anticipates danger from an environmental state. Similar to all qualia, conscious experience of pain cannot be fully explained in terms of neurophysiological events. Conscious pain is a complex perceptual and affective experience influenced not by the amount of the bodily lesion alone, but also by the whole personality of the sufferer. This often makes surgical, medical and psychological treatment of pain difficult and disappointing.