What comes closest to atheism in religious thinking?

Answer 1

Atheism is the non-belief in a deity of any sort. This precludes any religion that has a supernatural source of authority such as Christianity, Judaism, Islam, pantheism, Hinduism, even Satanism and Wicca (even though these are often touted by theists as being equivalent to atheism).

This leaves us with the philosophical "religions" such as Buddhism and Taoism and philosophies of life like Humanism and even North Korea's Juche. The Stoicism discussed in writings such as the Meditations of Marcus Aurelius with its ideal of dispassionate compliance with natural forces also has many close parallels with Buddhist thought.

Answer 2

If your thinking is at all religious, it can't be called any kind of Atheism. There are some religions, such as some schools of Buddhism, in which belief in God is seen as irrelevant.