How does uncertainty play into sin?


I have a question about uncertainty and sin. **I’m not talking about uncertainty concerning whether a sin is mortal or venial. **I’m talking about uncertainty whether something is a sin at all.

Consider the following case: A man in a grocery store decides to eat two or three grapes to test their ripeness before he purchases them. However, before he acts, he is in doubt about whether it is a sin. Without any priest around to consult, he plucks two grapes anyway and tries them. The grapes are sour; he doesn’t buy any at all that day.

When he gets the opportunity to consult a priest, he finds out that it was, in fact, a sin. Whether venial or mortal, is he guilty of any sin at all?

(Now I understand that in real life grazing in a grocery store perhaps might not be sinful. For all intents and purposes, however, please just assume it is.)


This relates to what the catechism calls “formation of conscience.” We are not born with perfect knowledge of what’s good or evil. When we reach the “age of reason” (usually taken to be about age 7), we do not suddenly have it all sorted out. In fact, we never, in this life, have it all sorted out. We are continually educating and clarifying our conscience.

When a situation arises, like the one you described, we make a quick decision, or perhaps just act without even thinking. Later we recognize that we may have sinned. For us, that can be an opportunity to learn, and to grow in virtue. Resolve to do better. Make restitution if necessary. Seek forgiveness. Give thanks. Go on living.

Here is a relevant section from the Catechism of the Catholic Church:
The Formation of Conscience

1783 Conscience must be informed and moral judgment enlightened. A well-formed conscience is upright and truthful. It formulates its judgments according to reason, in conformity with the true good willed by the wisdom of the Creator. The education of conscience is indispensable for human beings who are subjected to negative influences and tempted by sin to prefer their own judgment and to reject authoritative teachings.

1784 The education of the conscience is a lifelong task. From the earliest years, it awakens the child to the knowledge and practice of the interior law recognized by conscience. Prudent education teaches virtue; it prevents or cures fear, selfishness and pride, resentment arising from guilt, and feelings of complacency, born of human weakness and faults. The education of the conscience guarantees freedom and engenders peace of heart.

1785 In the formation of conscience the Word of God is the light for our path; we must assimilate it in faith and prayer and put it into practice. We must also examine our conscience before the Lord’s Cross. We are assisted by the gifts of the Holy Spirit, aided by the witness or advice of others and guided by the authoritative teaching of the Church.


If you have some reason to think that an act might be a sin, and you choose that act anyway, then it is at least a venial sin. Because you acted when your conscience was telling you that your act might offend God. In essence, you are acting as if you do not care if the act is a sin: “I will do this act, which I desire to do for whatever reason, even though it might be a sin.” That is a sinful decision, a sinful attitude.


NB: those with scruples can be in a very different boat than others here - they need to have a regular confessor who can also give them particular principles for them to follow. So as to act against any “undue fear” of sin. Against any scruples.


For those with a normal conscience, at least some moral theologians posit that one incurs a sin in such a situation because he should have at least exerted some effort to inform his conscience.

For the scrupulous, however, keeping in mind the absolute need to obey his confessor, the general idea is in situations like these, proceed with the presumption that it is NOT a sin and to NOT confess it. Again, the advice of the confessor trumps anything posted on Internet forums.


Thank you all for your thorough and thoughtful responses.


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