Rational arguments exert force on the human mind. The mind must assent to a logical line of thought once the premises are accepted. If you understand what ‘2’ means, you must agree that twice two is four.
Faith, however, is not the conclusion of a rational argument. There is no syllogism that runs A=B, B=C, therefore God exists, quod erat demonstrandum. There is no physical evidence of the claims of Christianity, only the witness of the church. The human mind is not forced to believe.
What then is faith? It is a holistic interpretation of all of reality – the material world, individual experience and human history – with the story proposed by the church as the key of interpretation, which the individual chooses to believe.
The believer and unbeliever look at the same realities, but give them different interpretations. The difference between belief and unbelief is not a new fact, but a new perspective.
Faith is primarily an act of will, not of the intellect. The intellect can only say “This interpretation of the world, this story that gives the universe its theme, is good to believe, it is not contradictory, it makes sense of the whole.” It is wrong to say faith is irrational, since the intellect of the believer judges faith as being a good thing and not repugnant to reason. Faith is however non-rational because the intellect cannot say “it is true” because the syllogism is not there.
Since the intellect is not forced, the will must make the leap from “it is good to believe this story” to “I believe it”. Faith is a choice.
When it comes to ordinary human beliefs on a lower level than the interpretation of all reality, holding to an opinion on the basis of will and not intellectual force is suspect: it is automatically a weak form of knowledge; at worst, a sign of stubbornness or shallowness.
But when it comes to the interpretation of all reality, some form of belief is necessary. There is no way to grasp the theme of the whole without a choice, and it is impossible to live a coherent life without choosing a meaning.