The term "Indian Philosophy" covers a comprehensive group of philosophical systems that originated in the soil of ancient India some three thousand years ago, and have developed from the primary and plenary spiritual insights of India's sages and seers. From the fundamental spiritual experience of seers a few insights were given to them; and from this "cluster of insights' each of the great sages has elaborated a particular view-point, seeking to order the relations between his particular viewpoint and the different doctrines of other contrasting viewpoints. This subsequent intellectual activity of explaining the basic "spiritual experience' in terms of differing philosophical view-points has given us the classical "systems," called Darsánas. The Darsánas can be divided into three broad groups: the orthodox (āstika), the heterodox (nāstika), and the Indian Materialist (cārvākā).