According to Wendy Doniger, the Puranic Shiva is a continuation of the Vedic Indra. Doniger gives several reasons for her hypothesis. Both are associated with mountains, rivers, male fertility, fierceness, fearlessness, warfare, the transgression of established mores, the Aum sound, the Supreme Self. In the Rig Veda the term 'śiva' is used to refer to Indra. (2.20.3, 6.45.17, and 8.93.3.) Indra, like Shiva, is likened to a bull. In the Rig Veda, Rudra is the father of the Maruts, but he is never associated with their warlike exploits as is Indra.