All true knowing comes from faith. Augustine put it this way: "I believe in order to know." The modern age replaced this ancient wisdom with the words of Descartes, cogito ergo sum, or "I think therefore I am." (This is a blatant heresy!) The sad fact is this kind of thinking eventually permeated the Christian church. We still haven’t shaken it to this day. Evangelicals buy into it every day when they argue for a kind of certainity of faith in ways that seem more like the conclusions of a mathematical formula than an appeal to the Word and the Spirit. This almost unchallenged approach seeks to "prove" the faith. But faith can’t be proven. If it is then it is no longer faith (Hebrews 11:1).
Descartes’ error was originally designed to help strengthen the Christain faith in intellectual battles brought on by the Enlightenment. In this case the cure of Descartes was worse than the problem. It divided knowledge into categories and created a kind of dualism that still cripples Christian thinking to this day. Whenever we speak of the head and the heart, as if they are quite different, we buy into this dualistic error. I hear this almost every day in common Christian expression. It is deeply engrained in us all. Regardless, it is a very significant error.
Michael Polanyi, a twentieth century philosopher, understood this far better than most when he wrote extensively about "personal knowledge." Said Polanyi, "All knowing of reality involves the personal commitment of the knower as a whole person." Read that sentence again, and again, and again.
So, we can’t know anything, in the full and true sense, without committing our entire being to the truth that we desire to know. This is why the word "know" has the connotation in Scriptrue of sexual intercourse. A man "knows" his wife in the way that the deepest form of knowledge is gained, through commitment. We know the Lord in this kind of knowing, thus the biblcial use of language here. This is why modern evangelism, with its simplistic formulas, fails so miserably. We are not inviting people to a proposition, or to a formula for success, but to a relationship of intimate, and eternal, knowing.
Does this mean that we reject reason? Not at all. Roman Catholic philosopher Peter Kreeft understands this (citing Pascal’s 110th Pensee) when he writes:
We know the truth not only through our reason but also through our heart . . . Those to whom God has given religious faith by moving their hearts are very fortunate, and feel quite legitimately convinced, but to those who do not have it we can only give such faith through reasoning, until God gives it by moving their heart, without which faith is only human and useless for salvation.
Kreeft is correct, at least up to a point, but he still depends overmuch on human reason. I do not deny that faith is reasonable but I do deny we can reason our way to faith. I do not think we can make disciples for Jesus by logic but this does not mean we are illogical in our thinking. In the end our logic and thought appear as "foolishness" to the modern Greek mind, especially the post-Enlightenment sort. Descartes may have set out to assist the faith of the Christian church but in the end he helped to nullify it in the minds not only of unbelievers but for generations of Western Christian believers. This can be seen in the process of how some Christians argue about the mind and its role in faith. Many conservative Reformed Christians make this error as frequently as non-Reformed believers.
We must believe that Christians should, and can, have the assurance of faith without the certainty of Descartes. I do not think most evangelicals undertand this well at all. A modern reformation must surely call for a return to this ancient, biblical, and pre-modern way of thinking about faith.