If you haven't checked it out - the Worldview Everlasting We've Got Answers page is one of the best resources on the internet for addressing tough theological questions (now they need to sort and organize it so we can click on a side bar and have questions about baptism or whatever show up). I have a feeling things I see on this site are going to get my mental juices flowing.
In particular I thought I would write about a question that dealt with whether or not Baptism was just a sign like circumcision. In particular there was this line - "I believe baptism, of the earthly water, is but a sign and indeed not baptism at all but a proclamation of one belonging to Christ for others to see, Then there is the comparison to Circumcision being a sign, or even a marriage.
Baptism is a "sign" like circumcision - but the thing that we forget is that "signs" by God are real and actually do things. When Jesus changes water to wine - this is a tangible change... and John calls it a "sign". When the official's son is healed - that is a tangible change - and it is called a sign. When one was circumcised in Israel, it wasn't just symbolic - it meant one was no officially part of Israel.
Signs in Scripture aren't just things that point to some higher reality (that Scriptural word is "type") - but they are things that are real and concrete. Yet we are so ingrained to think in symbolic ways that we neglect reality.
This is because signs aren't something we do or create - they are things that God accomplishes for us. Circumcision is a sign - a sign from God to the one circumcised that he was now part of God's covenant people. Signs are God working in us, thumping us and reminding us.
And Baptism thumps me all the time.