Many Christians claim that they have absolute certainty that they are the Children of God. They cite the following verse:
The Spirit himself testifies with our spirit that we are God’s children.
(Romans 8:16)
Is this possible? Is it possible for one very powerful mind to communicate knowledge to a non-omniscient mind?
Imagine the divine mind promises to send a divine spirit to flawlessly transfer the knowledge to a human mind. How can the human mind verify with absolute certainty that what they perceive to be the promised divine spirit is actually a divine spirit rather than an lying spirit or their own imagination?
Another independent mechanism must be introduced to verify with absolute certainty that what is perceived to be the promised divine spirit is, in fact, that divine spirit. Let’s imagine the human mind feels it has verified with absolute certainty, through some independent mechanism, that the divine spirit perceived is actually the promised divine spirit rather than some lying spirit or an imagined spirit. A problem immediately arises. That verifying mechanism must itself be verified by yet another verifying mechanism. And that second verifying mechanism must itself be verified by yet another verifying mechanism…ad infinitum.
Because the process of verification can never reach the level of justified absolute certainty by a less-than-omniscient and fallible human mind, we must conclude that no human can honestly claim to have absolute certainty that they are a child of God.
However, this does not exclude the possibility that a human mind can verify to a high degree that the information they perceive they are receiving is being transmitted by a divine mind. But this verification will not be based on an emotional confidence, but rather on a method that establishes the reliability of the information they are receiving. Previously unknown scientific knowledge and accurate and precise predictions would be a good start to establishing the reliability of the alleged transmission of knowledge from a divine mind.
(See also #08 and #31.)
Sufficient Reasons To Consider Leaving Christianity 