Why should one believe in Christianity? What evidence can one present to the skeptic or doubter or even the believer? Miracles are a popular one, but most have never seen one. Thinking back over the evangelism I have done and observed, the guilt argument is one of the most effective at making converts. Here is how it goes:
We are all sinners and guilty of breaking God's universal moral law. The evidence for this is the guilt we feel -- surely no one will deny that we each suffer from feelings of guilt at times in our lives. Hence we are each aware of being transgressors of God's law. Now the wages of sin are death, but the free gift of God is eternal life. One simply believes and repents and one will be forgiven one's sins. Moreover, this is right way to overcome our guilt.
I certainly believed this line of reasoning for many years. A favorite anecdote in sermons is that of a non-believer being driven by his or her overwhelming feeling of guilt to the forgiveness of Christ. What makes this powerful is that guilt is real, undeniable, and impacts everyone. If it is evidence for Christianity, then indeed one should pay attention.
But is it really evidence for Christianity? Is the argument sound? As I Christian I did not really think to question it; I knew what I wanted to believe and since it supported my beliefs I was happy to include it in my reasons for belief. Now, however, I only want reasons that hold water, and I fear this one does not. Here are the problems I see with it.
First, is it really evidence of a God-instilled moral code? As described in the Wikipedia article, "Guilt is an affective state in which one experiences conflict at having done something that one believes one should not have done." So guilt is evidence of internal conflict, of failing to meet one's own expectations. This conflict need not be between one's actions and God's laws. Rather, our moral expectations of ourselves can easily have purely natural sources. That is, guilt and feelings of right and wrong need not originate in God but are simply a component of our evolution as social beings. (I won't argue that here, but here is a post makes that case: http://www.steelcityskeptics.net/2008/09/08/secular-morality/.)
So guilt need not require the existence of a God-given universal moral code. But is it nevertheless a side-affect of this moral code, and so still useful evidence? The problem with this is the huge variability in guilty feelings, both between different people and in response to similar actions by the same person. Some people are highly sensitive to feelings of guilt; a minor infraction will send them into the depths of guilt. Others are impervious to guilt. While others may commit great crimes without guilt and then have great guilt for a small action. A measure with such variability is a poor indicator of a universal constant or a universal moral code.
A reponse to this is that those who willfully sin sear their consciences and lose their feelings of guillt. But is that really a satisfactory explanation for the variability of guilt? It does not explain why some feel guilt for certain small infractions but not other major ones. Nor does it explain why some are hypersensitive to guilt. It may be that some people can reduce their feelings of guilt through repeated efforts, but a better explanation for its variability among people is that just as physical and emotional attributes vary between people due to genetic and nurturing differences, in the same way sensitivity to guilt will vary.
As a final note, I wonder if it is true that Christianity offers an "answer" to guilt. Rather, from my observations of others and myself, it tends to enhance guilt, particularly in the case of small, inconsequential harms. I can say that from personal experience: as a child of about 5 I once stole a key from my grandfather's desk and then denied it to him when directly asked. I lost the key and so never returned it, but guilt from this sin stayed with me for many years and reoccurred most strongly during revival sermons. I wondered if that sin was the reason God didn't give me the gift of tongues, and other such blessings. Even though I many times asked Jesus to forgive that sin, the guilt from it did not go away. I never told anyone about it but finally, desperate to overcome the guilt, at the age of 15 or so I wrote a letter to my grandparents admitting and apologizing for my grievous sin against them. Then, in a letter to my whole family(!), they added a couple lines addressed to me thanking me for my admission. I think it was the annoyance that they would do that to me that finally overcame my guilt. But now that I look back at the experience, I think it was Christianity that harmed me by nurturing and feeding my guilt and keeping it in my mind as a possible reason that God may be witholding blessings from me when the guilt should have dissipated long before.
So to conclude, I do not believe that our feelings of guilt imply the existence of a God-given law. Rather guilt an important component in the interactions between social beings enabling others to forgive and so overcome wrongs. But guilt is also a useful tool for religions, both for making converts by offering people a way to overcome it, and then in keeping followers in repentance and submission by actually nurturing and spreading guilt.