Lingam, states Monier Monier-Williams, appears in the Upanishads and epic literature, where it means a mark, sign, emblem, characteristic. Other contextual meanings of the term include evidence, proof, symptom of God and God's power. The term also appears in early Indian texts on logic, where an inference is based on a sign (linga), such as if there is smoke, there is fire where the linga is the smoke. It is a religious symbol in Hinduism representing Shiva as the generative power, all of existence, all creativity and fertility at every cosmic level.