The Apostle Paul proclaims the ramifications of believing in the gospel in 1 Cor. 15:1 Now I make known to you, brethren, the gospel which I preached to you, which also you received, in which also you stand, 2 by which also you are saved, if you hold fast the word which I preached to you, unless you believed in vain.

If the gospel is something you must stand in and hold fast to, then where does your certainty come from?  For instance, how do you know Jesus died as it’s revealed?  How do you know he was buried?  What does your faith rest upon?  Must you have scientific evidence or archeological discoveries? 

Think about it this way—after all the eye-witnesses of Christ’s resurrection died off, what was to be the basis of the 2nd generation of Christians’ faith?  Another way to ask that question is this: What would God provide for his people of all time for them to have certainty regarding the events of the gospel? The answer is that he would provide an accurate, truthful, eye-witness account of Christ’s life, death, burial and resurrection. 

That is what God determined his people would need; and nothing would need to be added or deleted from it to increase certainty.      So if we seek certainty about Christ through some other means, we are inevitably eroding our faith, due to taking our eyes off of the God-breathed knowledge of Christ that is richly provided for us in the Scriptures.