Brittanyeah, Ron (Mlqurgw) has it right. Baptism by sprinkling isn't baptism. The very word "baptism" is a transliteration of a Greek word that, if simply translated, means "immersion." Scripture is rather clear that all of the baptisms in the New Testament church were by immersion. More than that, they were all done to believers. So the form of baptism performed in paedobaptist churches isn't a valid baptism.
That being said, some credobaptist churches have been moving away from the practice of requiring baptism of adult members. The Baptist church I attended in college has recently started the process of changing its bylaws to allow people who were baptized as infants to become members without being baptized as adults. I am currently becoming a member of the non-denominational church I now attend, and this church allows people to become members without being baptized. At our membership class, our pastor gave a simple statement of his logic which I think is the best explanation I've ever heard. He said, "if Martin Luther or John Calvin walked into our church and wanted to become members, we wouldn't want to turn them away."
The truth is, many sound believers in both ancient and modern times believe that infant baptism is valid baptism. I don't share this view, but the problem is that Scripture doesn't speak as forcefully here as it does on other topics. And to be honest, I'll accept a Bible-believing member of a PCA church as a beloved brother in Christ long before I will accept a liberal member of an American Baptist Church who believes in a false gospel.
I agree on the use of the Didache and other ancient documents in helping us to interpret Scripture, as long as they are never elevated to have the same authority as Scripture. They do make excellent commentaries on the Bible, if viewed in this light. And I say this as someone who is vehemently opposed to the apostate Catholic Church.
