In positive psychology, a meaningful life is a construct having to do with the purpose, significance, fulfillment, and satisfaction of life. While specific theories vary, there are two common aspects: a global schema to understand one's life and the belief that life itself is meaningful. Meaning can be defined as the connection linking two presumably independent entities together; a meaningful life links the biological reality of life to a symbolic interpretation or meaning. Those possessing a sense of meaning are generally found to be happier, to have lower levels of negative emotions, and to have lower risk of mental illness.