बिना किसी प्रमाण के किसी बात को सत्य मान लेने की धारणा को कौन सा शब्द परिभाषित करता है?

Choose the most suitable 'one word' for the given expression: 'A person who does not believe in the existence of God or gods'

Which one-word term is used to describe an animal or person that prefers to live, move, or associate in groups rather than in isolation, exhibiting a natural inclination for companionship?