We cannot reason or think our way out of true spiritual doubt, because we do not think or reason our way into it. There are a few mental states we can and do arrive at through a so-called rational process – ‘proving’ is another name for the process – but these mental conditions are few and, outside of the lecture hall, relatively unimportant aspects of the lives of virtually everyone.
The beliefs that matter to people, that is, that give direction to their emotions and energy, we sometimes refer to as convictions, and we may be convicted to doubt as well as affirmation. Convictions as so understood are almost entirely due to processes that are not rational in this strict sense. They find their genesis in environmental influences, peer pressure, genetic proclivities, and so on. Our political convictions are not birthed by our logic, although, once birthed, the various mental filters that define our ‘politics’ do most certainly guide the application of whatever forms of intelligence we possess. Our ethics, our taste, virtually all the important motivational elements congregated under the umbrella ‘personality’ arise from unknown depths and enlist our native cleverness into their service.
The same is true of our religion, understood as out spiritual convictions (including our doubts). Two people of equal intellect can look at the same tragic elements of human life. One sees them as confirmation of a belief in atheism; the other as elements to be incorporated into a trust in God. Both can argue eloquently in defense of their points of view, but simple observation reveals that no one has even been debated into convicted belief or disbelief in Christ, though many come to Christ and many fall away.
Is this an argument against evangelism? Not in general, but it helps us to understand why Paul avoided “lofty speech.” He had come to see that the infection of Christ passes, by the power and grace of the risen Christ alone, from spirit to spirit, and not from intellect to intellect.