My Catholic understanding of being guilty of sin involves knowledge that something is sinful, and, in the case of serious or mortal sin, the matter must be grave, done with knowledge and full consent of the will. I have been reflecting on the prayers in the Divine Liturgy where we ask God's forgiveness for sins voluntary and involuntary, know and unknown. While the Catholic Church talks about objective and subjective sin, the concept of unknown and involuntary sin, and its emphasis in the Liturgy, has profound implications. "Frequent confession" makes much more sense if sin is not only seen as a deliberate transgression of God's law. I have often thought that I did not have "matter" for confession, but defining sin to include involuntary and unknown transgressions has helped me to reconcile a sincere unawareness of sin (nothing deliberate to confess) and the expectation that a Catholic should be going to confession on a regular basis. Based on my understanding, would it be expected for Orthodox Christians, unaware of specific sin, to make a devotional confession, confessing any sins he or she may be unaware of? Or as in the Catholic Church, must there be "matter" for confession?