The premise establishes that human souls’ immortality is necessary for moral order. But the author mistakenly thinks this is sufficient for an element of that moral order to be true (the element of the bad always being punished).

The author does not assume or conclude that anything is an established fact. Although he describes what some cultures believe about moral order in the second sentence, he doesn’t suggest that these beliefs are true.

The author does not rely on a claim that immortality implies the existence of a moral order. Rather, the premise asserts that immortality is necessary for a moral order. Also, the conclusion does not assert that a moral order implies immortality.

Although the author describes two conceptions of a moral order in the second sentence, the author does not treat these as the same. These play no role in supporting the conclusion. The conclusion is based on the first sentence, which describes what is necessary for a moral order.

The author does not use circular reasoning. The conclusion asserts that immortality is sufficient for an aspect of moral order. This idea is not assumed in the premise, which asserts instead that immortality is necessary for moral order.