Case studies can be biased, social theories can miss critical variables, psychology models can explain a relatively small portion of real-world variance, logical conclusions can be tainted by limited knowledge of facts, mathematical models can be unknowingly incorrectly mapped to real-world phenomena, neuroscience studies can misinterpret signals.
If you rely exclusively on worldly methods of gaining knowledge, there is no way to be 100% sure of anything until you know everything there is to know. It is impossible to identify all the effects of what you haven't yet conceived, and you can never know just how much you haven't yet figured out. Thus, unless you are deceiving yourself you can never rule out your own ignorance as the chief explanation of your findings.
The divine way of attaining knowledge follows a different pattern. God himself tells you what is true in your mind and heart. You then choose to follow his counsel, and the promised outcomes result. Faith acted upon brings the promised blessings, providing supportive evidence of truth little by little with each step. A big difference for this path of gaining knowledge as compared to relying on our own understanding is that God does know everything, so by following His counsel we can avoid the major pitfalls that our own ignorance or self-deception would lead us to.