The concept of the age of accountability comes from Romans 7 in the Bible. In Romans 7, the apostle Paul states that there was a time when he "was alive apart from the law; but when the commandment came, sin sprang to life and I died." This is the idea that a period of time exists as a small child before one has the mental ability to grasp and truly understand the laws of God. During the time of innocence one is spiritually alive because God does not hold them accountable. A child who has passed the age of accountability is said to know the difference between right and wrong and to be capable of obeying the moral laws of God. Some Christian traditions believe that the age of accountability is the end of a period of early grace (prevenient grace, in Wesleyan traditions) which covers over the sins of those not capable of knowing the moral consequences of their actions (persons who, due to developmental disability, mental or emotional development, will never reach a sufficient level of abstract reason, are covered by this grace for life and are sometimes known as 'the innocents').
In Christian traditions that practice Believer's Baptism (baptism by voluntary decision, as opposed to baptism in early infancy), the ritual can be carried out after the age of accountability has arrived. Some traditions withhold the rite of Holy Communion from those not yet at the age of accountability, on the grounds that children do not understand what the sacrament means. Full membership in the Church, if not bestowed at birth, often must wait until the age of accountability and frequently is granted only after a period of preparation known as catechesis.
The time of innocence before one has the ability to understand truly the laws of God and that God sees one as innocent is also seen as applying to individuals who suffer from a mental disability which prevents them from ever reaching an time when they are capable of understanding the laws of God. These individuals are thus seen as existing in a perpetual state of innocence by the grace of God.