Traditionally, people believe that Nastik are the persons who do not go to temples or related places of worship. They also do not believe in God.

To differentiate between Astik and Nastik, we need to first understand the concept of Sanatan Dharma and Arya Samaj Dharma. People who believe in Sanatan Dharma consider God as separate from the self and worship him in the form of an idol. They believe in Dualism theory.

Arya Samaj followers do not do idol worship and believe in non-dualism and treat God and self as one.

Arya Samajis, therefore, will not go to a temple where the idols of Gods are placed. Being an Arya Samaji does not mean that the person is Nastik.

The word Nastik means someone who does not believe in God at all, therefore, he or she also does not believe in self as God is nothing but self. In medical sciences, these are the people who have no insight and will usually be suffering from depression and loss of self–esteem.(Disclaimer: The views expressed in this write up are my own).