Before discussing the book of John specifically, an explanation of what the gospels actually are, how they came into existence, and why they are universally accepted by Christians is needed. The gospels are broken down into synoptic (Matthew, Mark, and Luke) and one Johannite gospel (referring to the book of John). Putting the differences between the synoptics and the Johannite version aside for now, it should be noted that all of these books serve as the focal point of Christian belief, dealing primarily with the proclamation of redemption preached by Jesus. Upon reading the four different versions of the gospel story, the careful reader will presumably discover that more than a few minor "discrepancies" exist between the accounts. A natural reaction to this truth may include a combination of surprise, doubt, or confusion, since, after all, the Bible should (and is alleged) to be infallible truth. After investigating this topic more thoroughly, though, the reasons for why these inconsistencies exist become clearer.
Before delving into those reasons, though, one must first consider some key points regarding the gospels; Why, or what about these 4 books makes them divinely inspired, indisputable documents? And how did their writing come about?
Also, there are large selections of text that are "shared" (which could just as accurately be called plagiarism as we know it), and overlap between the accounts. Isn't plagiarism unethical, though? And (returning focus to the original issue at hand), how does one account for the incongruities among the gospels?
First of all, it should be pointed out that in order for these books to be divinely inspired, or canonical, there are certain criteria that must be met. First of all, the document in question must be in conformity with the principles of the church that one is dealing with...