Peter gives us a very important lesson based on his experience at the transfiguration of Jesus Christ. That the things that he is preaching are not based on myths but on his eyewitness testimony of seeing Jesus in the fullness of His glory! We can also be sure because of the prophetic word that has been given to us by God. So, the answer to our question after Peter calls us to live holy and effective for the gospel is: Yes. Yes, we can be sure!