Clerics DO NOT need to worship a god. Clerics can believe in a philosophy so strongly that they can manifest their powers.
— Todd Kenreck (@ToddKenreck) March 9, 2020
For the people in the back. "a cleric might instead serve a cosmic force, such as life or death, or a philosophy or concept, such as love, peace, or one of the nine alignments." – Dungeon Master's Guide
— Todd Kenreck (@ToddKenreck) March 9, 2020