"Everybody has presuppositions, everybody has preconditions for living their life, evaluating things, knowing what they know."
This quote comes from the soon-to-be-released video series, Basic Training for Defending the Faith, featuring the late Dr. Greg L. Bahnsen. Dr. Bahnsen gave the five lectures in this series to young adults to prepare them for a world that is hostile to their Christian faith. The above quote is the main point that he wanted these students to learn, and what they needed to learn, we must make sure that we remember also.
It should come as no surprise to any regular reader of American Vision material that we wholeheartedly agree with Dr. Bahnsen’s assessment. We all operate under and interpret through a preconceived set of unquestioned assumptions. Since we all don’t share the same starting assumptions, we all don’t share the same ending conclusions. This is why two different people can look at the same “fact” and come to two radically different judgments about the “fact.” Dr. Bahnsen takes it a step further though:
I want you to stop and think about this. When you wake up in the morning—you don’t assume anything now—you just have to start from scratch, deciding what you’re going to believe about life and about yourself.
Not content to be dealing with presuppositions on a theoretical level, he brings it down to a level we can all associate with. Every day we take numerous things for granted. If we didn’t, if we had to start each day “from scratch” as it were, we would never get very far in life; every day would be remarkably similar to the one yesterday and the day before that. Unless, of course, we left ourselves little reminders to give us a mental “jump-start” each morning. Interestingly, this is exactly the premise of the 2000 movie, Memento.
Leonard Shelby, the main character in the movie has a bit of a memory problem. He is suffering from anterograde amnesia, which means that he can’t create new long-term memories. His attention span is about 15 minutes, so unless he documents something that he wants to remember (by taking a picture with his ever-present Polaroid, or writing it down), he will certainly forget it. Although the film is far more complex than this and numerous internet sites are devoted to deconstructing it, this is enough information to suit our purposes. Leonard literally has to question everything every morning, he can’t bring anything from yesterday over into today in his brain, so he must find other ways to tell himself tomorrow what he thinks he knows today, right now. He writes notes to himself, takes pictures, and for the really important stuff, tattoos it to his body.
But as the movie unfolds, we (as the passive viewer) begin to see some leaps in Leonard’s logic that shouldn’t be made because we have the luxury of memory. Leonard’s system begins to break down because the very things that he relies on each day to get him one step further in his quest, are the very things that he cannot question. His assumptions, based on his notes, tattoos and photos, are faulty because he doesn’t have all the pieces, but he doesn’t know this, so he keeps on making erroneous conclusions, which are predicated on faulty assumptions. You see the problem? He can’t arrive at “truth” because he doesn’t begin with truth. No matter how genuine his beliefs in his deductions are, he still starts with error. And this is exactly the point that Dr. Bahnsen is making in his lecture. None of us are neutral, none of us begin each day as a tabula rasa, we bring presumptional baggage with us each morning. Not that this is a bad thing. “Starting from scratch” each day would be an incredibly counter-productive and inefficient way to live your life, just ask Leonard Shelby. The most important question to ask then, is: what is the basis for your starting point?
If a traveler decides to take a journey, and he has all the necessary equipment for the task, but he heads off in the wrong direction, all his skill and efforts will be in vain because he will not reach his planned destination. The same is true for the person who has a sharp and informed mind who takes his stand on the slippery slope of skepticism. His efforts, while marked with erudite arguments, will be without merit because his first step was in the wrong direction.
Leonard’s assumptions ultimately led him in some wrong directions, but, as Dr. Bahnsen teaches his students, we, as Christians, have the sure foundation of God’s Word to inform our assumptions. If we begin with the “beginning of knowledge”—the fear of the LORD (Proverbs 1:7), then we will be well-equipped to reach our destination. “Let no man deceive himself. If any man among you thinks that he is wise in this age, he must become foolish, so that he may become wise. For the wisdom of this world is foolishness before God” (1 Corinthians 3:18-19).
 In John Locke’s philosophy, tabula rasa was the theory that the (human) mind is at birth a "blank slate" without rules for processing data, and that data is added and rules for processing it formed solely by our sensory experiences. http://en.wikipedia.org/wiki/Tabula_rasa
 Gary DeMar, Thinking Straight in a Crooked World (Powder Springs, GA: American Vision, 2001), 105.