Expressions on the Proof of the Possibility of the Existence of God in Western Thought; Process, Methods, Problems and Epistemological Validity

In Western thinking, one of the most important proofs of God's existence is reasoning through possibility and necessity. Analyzing the process of its various expressions, the characteristics of each of those expressions and their distinctions, as well as evaluating their cognitive validity and achieving a criterion or a solution for evaluation, is the motivation of the current research. The result of this research is that all expressions have been presented in two ways or with two approaches: 1. Expressions through causality or causal explanation; 2. Expressions through description and explanation or non-causal explanations. On the other hand, by examining Aquinas's and Locke's expositions, which are examples of causal explanations, we are led to the conclusion that those expositions are either reasoning through occurrence or reasoning through non-causal explanation, not reasoning through possibility and necessity, nor reasoning based on causal explanation. Therefore, their epistemological validity is under question. On the other hand, Leibniz's argument and other explanations through non-causal explanation fail to carry epistemological validity, and it is not possible to achieve certain knowledge, even based on the correct assumption.