What Is a Presupposition?

[shotgun]

Consider this assertion:

"Dogs pee on brick walls."

How would you discover if this were true or not? You'd have to go out and find a dog peeing on a brick wall! But then, the skeptic would demand that you prove it really is a dog! So, first, you'd have to properly define "dog" by appealing to a dictionary. But wait says the skeptic, why is the dictionary authoritative? You then appeal to majority opinion! "But wait!" demands the skeptic, how do you know the majority really approved? So, you appeal once more to another thing...then another...then another and another...

In order to prove A, you appeal to B. In order to prove B, you appeal to C...in order to prove C, you appeal to D...and so on ad infinitum! You'll never be able to prove that Dogs pee on brick walls! (Scroungy mutts the world over bark happily at the news...at least until they read Van Til and find out that proof is possible after all!)

When a person makes an assertion that we as Christians disagree with, then...(in light of the above) we need to play the part of the skeptic. We need to dig into his assertion, and find out what lies beneath it. For example, in saying "Dogs pee on brick walls"...we are assuming what a dog is. We assume what a brick wall is. We assume we know what peeing is. Those are three "presuppositions" that must be true in order for the assertion to be true.

A presupposition is the term given to beliefs that stand behind various assertions. Any belief can be a presupposition. "There is ice in the freezer," presupposes the belief that the "freezer is working properly." It also presupposes the belief that "there was water in the freezer." So the belief: "There is water in the freezer" is a presupposition...a presupposed belief that is taken for granted and implied by the statement: "There is ice in the freezer."

When A is asserted, we need to look for what supports it (B). Then we need to look for what supports B, (C). We do this until we come to that final belief a person holds that is not authenticated by any supporting belief. If this belief is not self-authenticating in some way...then it is NOT the final link in the chain...we must keep searching.

In this sense (deconstruction), when we do "Presuppositional Apologetics"...we are searching for the ultimate or final presupposition that a person holds. The one belief that is at the very foundation of all his or her other beliefs. When we find it...we examine it, and see if it can authenticate itself, and see also if it is consistent with the rest of his beliefs.

I hope this helps clarify what a presupposition is, and how it is different from the mathematical concept of an "Axiom." (Presuppositions can be axioms, and axioms can be presuppositions...but the two aren't the same.)

[Thomas]

I hope this helps clarify what a presupposition is, and how it is different from the mathematical concept of an "Axiom." (Presuppositions can be axioms, and axioms can be presuppositions...but the two aren't the same.)

Please explain the difference.

[shotgun]

From James Nickel:

In deductive reasoning, certain general facts are assumed to be true. These facts are called postulates or axioms. - Mathematics: Is God Silent? pg. 34

To follow up, consider Burgess:

The format of an axiomatic-style proof procedure, for instance, is as follows. Certain kinds of formulas are admitted as axioms and certain kinds of inferences from premise formulas to a conclusion formula are admitted as (primitive) rules. A proof (of a given formula) is a sequence of formulas (the last being the given formula) in which every formula or step either is an axiom or follows from earlier steps by a rule. - Philosophical Logic pg. 11

The "axiomatic proof procedure" is only one method of many. As Burgess notes:

"...there are several formats for proof procedures (axiomatic, natural deduction, sequent calculus, tableaux, trees), all quite different in appearance. Yet all styles have some features in common. With all, a formal proof or demonstration is some kind of finite array of symbols, and it is decidable whether or not a given finite array of symbols is a proof of a given formula." - pg. 10

History has shown that this deductive attempt at proof fails miserably. (Nickel quotes Richard Courant and Harold Robbins. Additionally, he discusses Godel's theory at some length.)

These axioms are postulated and held as foundational in order to construct a demonstration of proof. They have a formal status.
While axioms must be presupposed in order for the deductive proof to be achieved...and can rightly be called "presuppositions" not all presuppositions hold the formal status of "axiom."

Nickel provides an example: The axiom in this case is: "All cats have whiskers." Then he postulates: Felix is a Cat. Therefore...we can say "Felix has whiskers." The axiom "All cats have whiskers" has a special, formal standing within this system of proof. Indeed if the axiom were not assumed, then it would be impossible to know if Felix has whiskers or not (unless we find Felix.)

When discussing a presupposition however...we're looking at what lies behind the claim "Felix has whiskers." For example...IF the claim were true, and Felix really has whiskers...then what would follow? What would necessarily be true in light of the truth of the claim? Well, the claim presupposes that Felix is real, that whiskers are real, that Felix is able to possess such things as whiskers...all these are presuppositions, but not necessarily formally stated axioms.

[Keith C]

When A is asserted, we need to look for what supports it (B). Then we need to look for what supports B, (C). We do this until we come to that final belief a person holds that is not authenticated by any supporting belief. If this belief is not self-authenticating in some way...then it is NOT the final link in the chain...we must keep searching.

In this sense (deconstruction), when we do "Presuppositional Apologetics"...we are searching for the ultimate or final presupposition that a person holds. The one belief that is at the very foundation of all his or her other beliefs. When we find it...we examine it, and see if it can authenticate itself, and see also if it is consistent with the rest of his beliefs.

I hope this helps clarify what a presupposition is, and how it is different from the mathematical concept of an "Axiom." (Presuppositions can be axioms, and axioms can be presuppositions...but the two aren't the same.)

Well-chosen axioms satisfy two conditions:-
1. None can be derived from the other axioms and the rules of the system, ie none is a theorem.
2. The axioms are complete and no other axioms are required for a complete system.
You are asserting 2 'facts' about presuppositions:-
1. Presuppositions are not complete, stand-alone assumptions, ie other presuppositions lie behind (can be used to justify or prove) those which are stated.
2. The ultimate presupposition(s) need(s) to be 'authenticated'.
In contrast, a consistent system of axioms stands by itself, without 'authentication'. The only question is what type of 'world' does it describe or apply to. ie is it euclidean geometry or some form of non-euclidean geometry?
In the same way, any set of axioms or presuppositions intended to describe the real world can be tested to determine whether those axioms make valid predictions about the world around us.
Why can't your ultimate presupposition be 'authenticated' in the same way?

I think you need to dig into the presuppositions which lie behind your 'facts' about presuppositions.

[shotgun]

Keith...self consciously reflect on your own position.

The questions you raise, while related, do not speak directly to the difference between axioms and presuppositions, and so I'll not reply here in order to keep the discussion focused. I'll reply over in the other thread:

viewtopic.php?f=32&t=1168&start=36

[OldDad]

Keith...self consciously reflect on your own position.

The questions you raise, while related, do not speak directly to the difference between axioms and presuppositions, and so I'll not reply here in order to keep the discussion focused. I'll reply over in the other thread:

viewtopic.php?f=32&t=1168&start=36

This is very interesting, but what does it have to do with the Scriptures? As believers in God and that He wrote the Scriptures Which are inerrant, makes the concept of presupposition theology just another stumbling stone. If God had said that the dog peed on the wall, then a dog peed on the wall. No need to argue "what is a dog or what is a wall", etc, etc. This as foolish as arguing Evolution with what God had written about the Beginning of all things. :OldDad]

[Keith C]

This is very interesting, but what does it have to do with the Scriptures? As believers in God and that He wrote the Scriptures Which are inerrant, makes the concept of presupposition theology just another stumbling stone. If God had said that the dog peed on the wall, then a dog peed on the wall. No need to argue "what is a dog or what is a wall", etc, etc. This as foolish as arguing Evolution with what God had written about the Beginning of all things. :OldDad]

You are obviously starting with the presupposition that the bible is inerrant. The presuppositionist position is that this assertion may not be a true axiom, but may be dependent on some other, deeper, assumption which you are making, even if you are not aware of it.

The other alternative is that god really does not exist, and that 'nature' itself is sufficiently complex that processes like evolution and even abiogenesis could proceed without help from a god.

You may feel that both of these alternatives are equally unreasonable. Do you have any reasons, or is that opinion just a gut feel?

[shotgun]

It is impossible for the Christian God not to exist...and to suggest otherwise is borderline blasphemy. It's a shame that so many Christian apologists are willing to suggest that God is only one possibility (albeit a strong one) among many.

We do presuppose the Bible as the infallible law-word of the God. In short...if the Bible were NOT true...then nothing could be true. Faith in the Bible (and what it claims about itself) is our ultimate epistemological foundation. (The Christian God is our ultimate metaphysical presupposition...but we couldn't know anything at all about Him without His own revelation of Himself.)

These issues are better addressed in the other thread.

To Old Dad...

I realize this kind of stuff might seem boring, and perhaps even unimportant to many Christians who have better things to do than sit around studying philosophy and apologetics.

Just as the Bible doesn't speak to specific techniques concerning how to use a buzz saw, or run a tractor, or mend a broken bone...apologetics is something we largely draw from implied truths...(though there are a few verses that speak directly to how we should conduct ourselves when doing apologetics.)

If you don't know the ins and outs of Presuppositionalism...you can still be a good Christian. If you don't know all there is to know about farming, you can still be a good Christian...same for any field out there.

That doesn't mean these topics shouldn't be discussed, debated, and clarified.

[JLVaughn]

You are obviously starting with the presupposition that the bible is inerrant. The presuppositionist position is that this assertion may not be a true axiom, but may be dependent on some other, deeper, assumption which you are making, even if you are not aware of it.

No Keith,

OD's presupposition is that he understands the Bible and his understanding is inerrant.

To define a presupposition, think axiom, but allow that a presupposition 1) is rarely mathematically or logically precise, 2) may contradict other presuppositions, 3) may be derivable in whole or in part from other presuppositions, 4) may be based on reason, emotion, or experience, 5) may be discarded and replaced by other presuppositions, but typically at great emotional cost.

Blessings.

[jms]

Shotgun,

Let me try to put this into my own terms to see if I get what you're saying. The argument you made about Felix having whiskers can be written in predicate calculus as:

1. forall X. cat(X) => hasWhiskers(X)
2. cat(Felix)
-------
hasWhiskers(Felix)

Axiomatically, this works just fine. However, it could be that the meaning of cat(X) is "X is Louis XIV", and the meaning of hasWhiskers(X) is "was the king of France in 1700". The problem with an axiomatic system all of the associations between the symbols and the real world, and hence all of the conclusions, are not part of the axiomatic system. We read all that stuff into it.

The idea of a presupposition is that it's actually connected with reality. So then when we read the axioms, we ask what cat(X) means in the real world, and what hasWhiskers(X) means, and then we start asking whether we believe cats exist and can have whiskers. But it sounds to me like all we're doing is adding more axioms.

forall X. cat(X) => exists(X)
forall X. cat(X) => canHave(X, whiskers)
forall X. not canHave(X, whiskers) => not hasWhiskers(X)

and so forth. But of course, now we start asking what exists means, and canHave means. Asking these questions has not gotten us any closer to connecting our statements with reality, and no amount of asking will help us. In order to answer these questions, we have to somewhere along the line give a definition of an atom or predicate in terms of the real world, and this can't be done with language for the same reason that it can't be done with mathematics. This question of how to actually define an object belongs in our upcoming thread about predictive coding, but suffice it to say for the moment, I don't see how presuppositions are anything more than an infinity of axioms we add to try to make language do something it can't do.

[Keith C]

To define a presupposition, think axiom, but allow that a presupposition 1) is rarely mathematically or logically precise, 2) may contradict other presuppositions, 3) may be derivable in whole or in part from other presuppositions, 4) may be based on reason, emotion, or experience, 5) may be discarded and replaced by other presuppositions, but typically at great emotional cost.

Shotgun went a little further. He required that presuppositions be consistent.
Also, I suspect that one valid idea behind the search for 'ultimate presuppositions' is the realization that the imprecision of language requires a large number of other presuppositions which are essentially definitions of terms.
Not sure about the rest.

[JLVaughn]

Keith,

No one has consistent presuppositions. That is why we are occasionally surprised to see what we expect.

Consistent presuppositions is probably a reasonable desire and goal. But it is not an inherent human trait.