Final answer:
Natural revelation is the understanding of God through nature and its laws, while divine revelation involves direct communication from God, often through sacred texts such as the Bible. Non-believers may question the validity of these revelations due to the lack of personal experience or skepticism towards the divine origin of sacred texts.
Step-by-step explanation:
Natural revelation refers to the understanding of God's existence through the observation of the natural world and reasoning about it. According to Theistic Natural Law Theory, God made Nature, the Natural Laws, and humans, providing them with reason to discover these laws. This indirect knowledge through nature's existence as caused and sustained by God is an idea supported within Thomas' empiricism, which posits that we cannot directly grasp God through reason, but can infer God as the Necessary Cause of what we see in the world.
Divine revelation, on the other hand, works through direct communication from God to humans, often through sacred texts. The argument from Revelation is that God reveals His existence to humanity through these texts, which are believed to be divinely inspired. One such example is the Bible, which asserts God's existence and is taken as truth by believers due to its divine origin.
However, these methods raise questions for non-believers or skeptics. If someone has not experienced a religious experience or does not accept sacred texts as divinely inspired, they may question the truthfulness, accuracy, or sufficiency of these experiences or texts to confirm the existence of a supernatural realm or deity. Addressing skepticism, especially when considering alternate explanations for religious experiences, is a significant challenge in validating theistic claims.