We baptize babies. We baptize children. We baptize adults. We do not re-baptize anybody. The reason we do (or do not) such things is because we take God’s grace seriously.
Baptism is primarily an act of God, and only secondarily a human act. Simply put, in baptism God says “Yes” to the one being baptized. In a mysterious way, each of our baptisms is a participation in Jesus’ own baptism where the voice from heaven proclaimed “You are my Son, whom I dearly love; in you I find happiness” (Luke 3:22). These words then are spoken over all the baptized. These words are properly said over persons regardless of age or capability to understand. This means we baptize some people without their permission and without their ability to faithfully respond (I am talking about persons such as infants). Although, of course, we will teach and encourage those infants as they become children and young adults how to respond faithfully to the grace given by God in their baptism. We will even mark this response with an act we sometimes call “confirmation”. This is a fancy phrase for the act, simply put, of responding to God’s “Yes” with our own “Yes”. Thus, baptism and confirmation belong together — and in the baptism of one who is able to respond for themselves, in fact, both acts are done simultaneously. However, it is important to note the distinction. Baptism happens only once. God is faithful, period. When God says “Yes” at baptism, it never needs repetition. However, humans are often less faithful. Our “Yes” on occasion will need a reaffirmation; this means that “confirmation”, or said in another phrase “remembering our baptism”, is done over and over again in a person’s life.
Therefore, we baptize babies; we do not simply dedicate babies (although, of course, a part of baptism is “dedicating” the child.)
Neither therefore, do we simply christen babies. Christening in its origin means “giving a Christian name”. In some places a middle name is given at baptism. However, in common use “Christen” has often come to be a synonym for “baptize”. We will discourage such usage in order to avoid misunderstanding as well as not to diminish the significance of baptism.