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11. The importance of presuppositions
We have earlier seen how the term presupposition refers to fundamental assumptions in an argument, claim, or simple utterance. These assumptions aren’t taken randomly by anyone, but they are a reflection of their worldview. They come at the most basic level of their network of beliefs. Presuppositions form a wide-ranging, foundational perspective (or starting point) in terms of which everything else is interpreted and evaluated. As such, presuppositions have the greatest authority in one's thinking, being treated as your least negotiable beliefs and being granted the highest immunity to revision.
When talking with unbelievers, while there may be some discussion of science, archeology or the like along the way, discussion will always, always, come down to matters of ultimate authority - i.e. the foundation of your entire belief system. The intended conclusion of a line of argumentation will also be the presuppositional standard, which governs the manner of argumentation for that conclusion - or else the intended conclusion is not the ultimate authority after all. (For further discussion of this point, see Greg Bahnsen, Van Til’s Presuppositionalism, in Penpoint Vol. VI:1.)
A presupposition is not merely some basic assumption. It is much more than that. Think about it this way. In September 2001, the Twin Towers in Manhattan, New York, came down. There were thousands of people around the towers. The population of Manhattan is 6 million; most of the major national and international TV networks were covering what was happening live; it was probably one of the most watched events in human history. We have all seen the footage, we have read the news, yet nearly two decades, tens of documentaries, and hundreds of books later, people are still in disagreement about what actually happened. My point isn’t to take one side or another but merely to point out even when something is witnessed to that extent, it still doesn’t settle the matter, because every piece of information which comes to us will be interpreted according to our presuppositions.
Think about something even more mundane. Why do you drink water when you are thirsty? You will say: Because water quenches my thirst. But how do you know that? Well because every time I have been thirsty in the past and I drank water, it quenched my thirst. Now if you think about it, this can be true if and only if we live in a world where the past and the future are correlated. What happens in the past under certain conditions would be repeated in the future if these conditions were not changed. That is to say, we live in an orderly, law-like world. If we were to live in a random-chance universe, then whatever happened to you when you drank water in the past would have nothing to do with what water might do to you now or in the future. All bets are off and anything could happen. In philosophy this is called the problem of induction. It is presupposed by everyone who engages in any kind of activity, from drinking water to landing on the moon. Christians can account for and make sense of induction based on God’s revealed Truth. God has created the universe (Genesis 1:1-3, Colossians 1:15) and He sustains His creation (Colossians 1:17, Hebrews 1:3). He orders us to care for the creation (Leviticus 18:26-28), to have dominion over it (Genesis 1:28), and to use it for His glory. He also promised seasons would follow one another (Genesis 8:21-22). So as Christians we can at least start to make sense of the continuity of laws and the relationship between past events and future events, but how would unbelievers account for it?
The atheist philosopher Bertrand Russell wrote: “The general principles of science, such as the belief in the reign of law, and the belief that every event must have a cause, are as completely dependent upon the inductive principle as are the beliefs of daily life. All such general principles are believed because mankind have found innumerable instances of their truth and no instances of their falsehood. But this affords no evidence for their truth in the future, unless the inductive principle is assumed.” (Bertrand Russell, The problem of philosophy. On Induction). For an unbeliever he would have to assume (presuppose) a principle that is at odds with his idea of a random chance universe, and there is no justification if unbelievers try to appeal to experience. As Russell says, “The inductive principle, however, is equally incapable of being proved by an appeal to experience. Experience might conceivably confirm the inductive principle as regards the cases that have been already examined; but as regards unexamined cases, it is the inductive principle alone that can justify any inference from what has been examined to what has not been examined” (Ibid.).
Here’s the irony. Unbelievers can make no sense of or explain “induction” - or anything else for that matter - yet they take induction for granted. It is not argued for but assumed; it is expected to be true; it’s almost inconceivable, if it were not true. This is a presupposition, a basic assumption about the world; it is taken for granted, there is no argument for it, it is something by which we interpret the rest of the world. It is your ULTIMATE authority.