
Adi
Shankara (or Shankaracharya), who is reputed to have started the system
of worshipping five deities. He is founder of the Advaitin School of Vedanta
philosophy (monism), which underpins the widespread notion that all deities
are equal.

Madhva
(or Madhvacharya). There has been some tension between the various denominations
and schools of thought, most often between Vaishnavas and Shaivas/Shaktas.
There has also been much theological controversy. Discussion and debate
is an important and welcomed aspect of Hinduism. Madhvacharya was a Vaishnava
theologian and most strongly contested Shankara's monistic doctrine. Madhva
propounded that Vishnu is Supreme. Some teachers within the Shaivite and
Shakti traditions have also propounded that their respective worshippable
lords are the Supreme (God). Smartas consider all deities equal, simply
different attributes of an impersonal Supreme.
There is a fourth mainstream Hindu community. For its emphasis on smriti, its followers are known as Smartas. They are traditional, very strict about rules and regulations, and emphasise the universality of Hinduism by distancing themselves from the exclusive worshippers of Vishnu, Shiva or Devi.
They worship five deities – Vishnu, Shiva, Devi, Ganesh, and Surya, as introduced by Shankara. The ten orders of sannyasa (dasanam), founded by Shankara, also follow the same system of panchopasana (five types of worship). Some of these sannyasis (renunciates) tend towards special veneration of Shiva, of whom Shankara is considered an incarnation.
The Smarta tradition is a relativiely new development in Hinduism. Many Hindus may not strictly identify themselves as Smartas but, by adhering to Advaita Vedanta as a foundation for non-sectarianism, are indirect followers. Nonetheless, other traditions dispute the claim that the notion of an impersonal God is the only basis for non-sectarianism. These controversies over the nature and identity of the Absolute were spearheaded by prominent theologians.
"In these three worlds, it is only the association of saintly people that serves as the boat to carry one across the ocean of repeated birth and death."
Adi Shankaracharya