In the thread about the role of Ishwara it was noted that an exclusive approach to God can end up in fanaticism. Yet the opposite extreme, to just lump everything together into one insipid mess is not good either. In the Smarta sampradaya we have a practice that attempts to eliminate both problems--the panchayatana puja. We believe it was established by Shankaracharya himself.
According to the Digvijayas the situation was not good at that time. There were many sects and philosophies that misinterpreted or were completely against the Vedas. Amongst the astikas much energy was misspent in arguing over whether Shiva Bhagawan was superior to Vishnu Bhagawan or both were inferior to Mataji etc. To alleviate this and to get people thinking of the Advaita bhava, this puja was started.
In this puja all the five major deities of Sanatana Dharma are worshipped:
Shiva, Vishnu, Devi, Surya and Ganesh Bhagawans.
There are five forms of arranging Them: