By C.L. Bolt
Presuppositions are beliefs that people take to be the case as they come to some other belief or piece of evidence. A person who comes to the barber shop with a credit card and wants a haircut presupposes that the barber shop accepts credit cards as a means of payment. Note that presuppositions might be true or false in this sense. To ”presuppose” something is to “suppose” that something “beforehand;” “pre-suppose.”
People have all sorts of presuppositions as you can likely imagine. However when we speak of presuppositions in this treatment of covenantal apologetics we will speak of them mostly in terms of beliefs which are supposed beforehand that are held very strongly. In fact, we might want to call them “commitments” rather than beliefs, since beliefs often tend to be thought of as having less significance or being less firmly held or less likely to be true than the things we are really strongly committed to. Presuppositions are commitments that are held at the fundamental level of the thoughts or reasoning of people.
For example, someone could be very strongly committed to the idea that global warming is false, and think by virtue of this presupposition that cold weather indicates or confirms that global warming is false. However, a person who presupposes that global warming is true will take the evidence of a cold day filled with snow in an unlikely place to be evidence of global warming; the polar icecaps are melting and are causing the oceans to drop significantly in temperature. Or, the person who presupposes that global warming is true could just see the evidence and think that it seems to be contrary to his or her presupposition, but nevertheless rejects it as being anything substantial or does not view it as overturning his or her presuppositions. The point here is to illustrate what a presupposition might look like, and to illustrate as well that presuppositions affect how we view evidence.