A friend passed this onto to me a little while ago, when we were discussing a separate thread. It applies here.
The great Orestes Brownson said that when a baptized child reaches the age of reason and a) fails to make an act of faith in the true religion or b) makes an act of faith in a false religion, such as taking part in non-Catholic worship, he loses the habit of faith.
Orestes Brownson explains:
"The church teaches, as we have learned her doctrine, that the infant validly baptized, by whomsoever the baptism is administered, receives in the sacrament the infused habit of faith and sanctity, and that this habit (habitus) suffices for salvation till the child comes to the use of reason; hence all baptized infants dying in infancy are saved. But when arrived at the use of reason, the child needs something beyond this infused habit, and is bound to elicit the act of faith. The habit is not actual faith, and is only a supernatural facility, infused by grace, of eliciting the actual virtue of faith. The habit of sanctity is lost by mortal sin, but the habit of faith, we are told, can be lost only by a positive act of infidelity. This is not strictly true; for the habit may be lost by the omission to elicit the act of faith, which neither is nor can be elicited out of the Catholic Church; for out of her the credible object, which is Deus revelans et ecclesia proponens, is wanting. Consequently, outside the church there can be no salvation for anyone, even though baptized, who has come to the use of reason. The habit given in baptism, then, ceases to suffice, and the obligation to elicit the act begins."