Now, with those thoughts in mind, imagine what it would have been like to live in the first century shortly after Jesus' ascension into heaven. The book of Acts makes it clear the gospel message was spreading rapidly (Acts 8:4). People all over the world were learning about Jesus the Christ through a message that was primarily communicated through spoken words. No doubt there were some unintentional inaccuracies being spread by zealous disciples (just like in the Telephone game).
If the gospel message was only communicated orally, then it would be destined to gradually change as it was transmitted from one person to the next. In such circumstances, those who had not heard the message directly from Jesus, the apostles, or others who were inspired, would have rightly had doubts about the accuracy of what they were hearing.
But, thankfully, the gospel message was not just transmitted by speech. It was also written down by divinely-inspired men in order to accurately record and preserve the truth for all-time. We can see that Luke penned his account of the gospel for this very purpose: Luke 1:1-4 - "Inasmuch as many have taken in hand to set in order a narrative of those things which have been fulfilled among us, just as those who from the beginning were eyewitnesses and ministers of the word delivered them to us, it seemed good to me also, having had perfect understanding of all things from the very first, to write to you an orderly account most excellent Theophilus, that you may know the certainty of those things in which you were instructed."
Many of the oral teachings and written testimonies being circulated in Luke's day, even from eyewitnesses, were insufficient due to their incompleteness and imperfections. Thus, Luke, an inspired author (which explains his complete understanding of the subject matter), wrote this account that Theophilus, and future readers, could know assuredly of the things in which they had been instructed. This assurance of accuracy when it comes to the Bible text is extremely important since man's faith is based upon the testimony of the written word (John 20:30,31).
Oral communication is a wonderful tool, but it often lacks the accuracy and permanency of written words. Praise be to God for the Bible, His inspired, written communication for man. We can know the certainty of the things recorded therein!