Query:

I have been arguing with my friends about the existence of God.  How can we weigh the evidence for and against a position?  How do we know how much evidence is needed to prove a position?  It’s impossible to prove all of the arguments for a position.

Reply:

A complete answer to your questions today would require a library, not a blog post!  But let me see whether I can say anything helpful, and yet brief.  I know how you have wrestled with your own doubts too.

In one sense, your question cannot be answered.  There isn’t any rule, any procedure, or any algorithm which can weigh evidence and say “Okay, you have enough now.”  The only instrument we have is our own minds.  So there is a subjective element even in assenting to what is true independently of our minds.

In another sense, though, your question can be answered.  Ultimately, the decision to assent to a truth comes down not to whether there is “enough,” but whether the grounds for assent are more compelling than the grounds for refusing assent.  Sometimes this can even mean whether our minds are better able to endure not having answers to one set of questions than not having answers to another set of questions.  The reality of God provokes questions like “Why is there evil?”, some of which we can answer and some of which we cannot.  But His nonexistence would provoke questions like “Why is there good?  Why is there anything at all?”

The grounds for assent can themselves be weighed, and the mind has a number of resources for doing so.  One, of course, is reasoning, but reasoning by itself is not enough, because except for the first principles of all reasoning, the faculty of reason cannot supply its own premises.  These come from other sources, such as conscience, experience, and authority.

Conscience, for example, gives me grounds to believe in God, because a law requires a lawmaker.  The experience of grace gives me grounds to believe, especially in the sacraments, for in Christ things become possible which I cannot do by my own power, such as breaking free of habitual sin.  Authority is reviled these days, but sound authority actually extends my reason, conscience, and experience, because minds like yours and mine don’t operate in a vacuum – we are not solitary but social beings.  I would be a fool to disbelieve in the existence of China because the reports of people who have been there as “a mere argument from authority,” and in the same way, I would be a fool to carelessly disregard the treasure of wisdom in the Scripture and Tradition of the Church.

Practical certainty -- what used to be called moral certainty -- does not mean that I have come to a point at which no further counterargument can be found or imagined, but that I have come to a point at which it is reasonable to assent.  Assent is more than just intellectual, because it involves an act of the will.  I must not only believe, but trust.  I must allow myself not only to hold a belief, but to say “Yes!” to it.  As the apostle James says, the devils believe – and tremble.  Assent means that we believe, we accept – and, in the case of assent to God, that we rejoice.

You speak of believing in a “position,” but there is a great difference between believing in an abstract proposition and believing in a person.  Granted, I must believe in certain propositions in order to believe in a person; for example I must believe that the person is real and not a figment of my imagination.  Even so, personal knowledge exceeds abstract knowledge.  Believing and assenting to God is more like falling in love with someone and marrying her than like believing in Newton’s Three Laws of Motion. 

Even in the experience of love, over time I learn more and more about the beloved.  As I do so, I come to trust what I know about her more and more – I trust her more and more – and I come to trust my trust, so that I no longer doubt her.  Finally, in marrying, I trust myself to her, because marriage is a mutual gift of self.  It isn’t for nothing that Scripture describes our relationship to God Himself as a marriage, and promises a wedding feast.  But He is not the bride but the bridegroom.

Rather than putting an end to new knowledge, trusting myself and opening my soul to the beloved opens up the possibility of even greater knowledge.  The knowledge available from outside of the relationship of trust is very limited, but the knowledge available from inside of it the relationship is deeper and more intimate.  Every husband and wife know this.  So it is, I think, with us and God.

Of course God knows us through and through already.  He doesn’t have to learn about us, but we have to learn about Him.  In this life that knowledge is by faith, which is a kind of knowledge because it carries with it its own experience and authority; it is not just abstractly thinking something about Him but having a foretaste of Him, for as the letter to the Hebrews declares, “Now faith is the substance of things hoped for, the evidence of things not seen” (a passage the meaning of which is blurred in some translations).  Yet even so, this “kind of knowledge” is not the same as seeing Him.  It is more like seeing an image in a mirror.  In the next life, faith will no longer be needed, because we will behold Him face to face.  We will know as we are known.  In that hope we live, groaning with anticipation, because it is not yet fulfilled.

It staggers me that our Lord was not content to be an Unknown God, as in the inscription on the famous Athenian altar.  It stuns me that He was not content merely to send messages, but came among us.  It leaves me in awe that the Creator of the Universe did not abhor the Virgin’s womb.