Presuppositional apologetics is a form of Christian apologetics, primarily in the Calvinist tradition, that asserts that the acceptance of either the proposition "God exists" or the Biblical inerrancy is necessary in order for the world to be intelligible. Presuppositional apologetics typically rejects Thomist apologetics, which accepts the rules of logic prior to arguing for the existence of God. There are two historically distinct branches of presuppositional apologetics: Van Tillian presuppositionalism and Clarkian presuppositionalism, attributed to their namesakes, Cornelius Van Til and Gordon Clark.
"[We] should present the biblical God, not merely as the conclusion to an argument, but as the one who makes argument possible (...)"
- "The battle is not over evidence but over philosophical starting points: presuppositions. As Christians, we should never put away our axiom—the Bible—when discussing truth with others. This would be like a soldier going into battle without any armor or weapons. "
- "By demonstrating that unbelievers can not argue, think, or live without presupposing God, presuppositionalists try to show unbelievers that their own worldview is inadequate to explain their experience of the world and to get unbelievers to see that Christianity alone can mkae [sic] sense of their experience. "
The Transcendental Argument for the existence of God (TAG) is often considered a claim of presuppositional apologetics, though it is also used (in a somewhat different form) in Thomist apologetics. The argument has also associated with the claim that "Atheists know there is a God".
Basic Forms and Principles
Van Tillian Presuppositionalism
Van Tillian presuppositionalists treats the Bible is the sole arbiter of whether a proposition is true or false; as a result, all knowledge claims must be given Biblical justification. They cannot be known independently of the Bible.
The laws of logic and causality are considered as true but not foundational. Rather, apologists assert that those propositions are true if and only if the truth of the Bible has been granted. In this argument, the basic laws of logic must be supported by Biblical justification.
- Skeptic: Is the logical law of modus ponens the case?
- VT Apologist: Of course modus ponens is the case. It is one of the most important rules of logic.
- Skeptic: But isn't modus ponens, given its standing as a rule of logic, foundational?
- VT Apologist: No. Only the Bible is foundational. Modus ponens can be used to check the coherence of other propositions with the truth of the Bible.
Apologists claim there are conclusive proofs of the existence of God based on logic. However, Van Tillian presuppositionalism draws a distinction between proof and persuasion. Van Til recognizes that many of these proofs are not pragmatically persuasive. Van Til asserts that this is because the skeptic rejects the epistemological framework (Platonic epistemology) necessary for the acceptance of those proofs. Van Til advocating Platonic epistemology as the only epistemology that is Biblically defensible.
Plato's epistemology differs from Van Til's in one very important respect: Plato does not accept the Bible as the foundation of his epistemology. For Plato, the Forms are foundational, and there is no text which can communicate the forms to individuals. For Van Til, the Forms are secondary to the belief in God and the truth of the Bible, and belief in the Forms is justified by the Bible.
Transcendental argument and variants
- Main Article: Transcendental argument
While presuppositional apologetics is as much a system of belief as anything else, it is sometimes presented as an argument to non-believers as: 
- All we experience is grounded in the laws of logic.
- The Christian worldview alone adequately explains and accounts for the laws of logic.
- Therefore, all we experience cannot be explained or accounted for outside of the Christian worldview.
Since the second premise is disputed, the more fundamental form of the argument is: 
- Logic (or reason or knowledge, depending on the variation used) requires justification.
- Atheists cannot provide a justification.
- Therefore, God is necessary in providing a justification.
Of course, there are multiple problems with this argument. Eric Hovind and Sye Ten Bruggencate have similar variants of this argument that they follow in a checklist/script fashion. Their fundamental aims are to question a non-believer's basis for their reason and their reliance on their senses, and then launch into the non sequitur that God or the Bible resolves the supposed difficulties. 
The transcendental argument runs:
- If there is no God, no knowledge is possible.
- Knowledge is possible.
- Therefore, God exists.
Van Til popularized a version of TAG, based on the role of the reciprocal relationships of the ontological trinity. There is some confusion about the exact structure of the argument, as it varied throughout Van Til's own writing. However, the traditional formulation is that the reciprocal relationships of the Trinity, being higher order relationships that exist outside of a relationship to the physical world, are the fundamental basis for logical relationships, and so reason is contingent on the existence of the Trinity. These arguments are rather strange because it claims the Biblical account of God to be foundational for the laws of logic, instead of allowing the laws of logic to be primitive. This version of the argument is problematic, because the relationship between entities is a synthetic statement while the laws of logic are analytic statements (the distinction was proposed by Kant).
Clark treated the truth of the Bible as though it were one of the axioms of a logical system. Other logical principle may be foundational, as long as they are compatible with the Bible. Clark asserts that the worldview that results from the acceptance of the Biblical axiom can be tested for consistency and comprehensiveness. Clark focused on demonstrating that there are no discrepancies or contradictions which can be produced by accepting the Bible as true, and embraces the possibility of using formal logic as a method for testing the propositions in order to ensure this. Because the Bible is foundational to a logical system, if any other logical rule produces any contradiction, then that logical rule must be rejected.
The idea that the Bible should be examined for possible contradictions draws some criticism from the Van Tillian branch, because they feel that the Bible should not be weighed against logical axioms. If an axiom is found to, hypothetically, demonstrate a contradiction within the Bible, then the problem is the axiom. Because Clark accepts that the laws of logic have bearing on falsifying the Bible, Van Tillian's often argue that this is not a genuine sort of presuppositionalism, and that it puts the laws of logic on the same foundational basis as the Bible.
God as an explanation for logic
- Main Article: Argument from ignorance
The final step in the persuasive argument is an argument from ignorance and God of the gaps. There may be other justifications for logic that are beyond our current understanding. The argument is reminiscent of the Natural-law argument and "Evolution is false, therefore God exists", which both suffer from the same problem. The apologist still needs to explain how the Bible can justify knowledge without using any other hidden presuppositions, which will be difficult to show.
The explanation also suffers from being a bigger mystery that what is supposedly explains.
In debates, apologists implicit assume that one and only one person has the correct "world view". They attempt to undermine other world views in an attempt to prove their own view. This is a false dichotomy.
It also falsely implies that to make use of logic, we require a "justification". We may assume the pragmatic position that logic is useful and leave it at that.
Treating synthetic propositions as foundational
Presuppositional apologetics treats a non-tautological synthetic existential claim (i.e. 'God exist' or the Bible) as primitive. It is generally accepted, in logic, that only universal claims (all x are y) and tautological claims (some p is p) can be primitive. Presuppositional apologetics is founded on defining God into existence and dogmatic claims:
- "To be a presuppositionalist is to redefine the world in such a way that you cannot possibly be wrong and then congratulating yourself for being so right. It's not an argument fit for an intelligent honest person. It's an argument fit for a coward."
In modal logic, existential claims about logical possibilities (like 'God exists') are generally believed to be true in at least one possible world and false in at least one other possible world. Because they are generally accepted as being false in some possible world, they are not considered necessary truths. Only necessary truths can be primitive.
The argument is an attempt to prove a matter of fact using only abstract logic, however it is impossible to demonstrate any matter of fact by this method.
The belief in God is considered a primitive by the apologist and therefore not falsifiable. There is no possible argument to change an apologist's mind. It is difficult to claim something is knowledge about reality and at the same for it to be unfalsifiable.
Apologists claim absolute certainty for presuppositionalism, but psychology tells us there humans are always prone to error, both in perception and cognition. Therefore they are making an impossible claim. It is always possible for people to be wrong.
Dismissing secular knowledge
- Main Article: Atheists cannot know anything
Apologists such as Sye Ten Bruggencate claim that the possibility that a person is wrong about any or all of their beliefs is equivalent to "knowing nothing".  This whole point by apologists is a red herring since they may destroy their opponents system but they still have not proved the validity of their own view. It is also a tactic to keep skeptics on a defensive footing in debates and prevents proper analysis of the apologist's views. 
Bible is disproved by empiricism and science
The Bible makes claims that are empirically falsifiable, and those claims are not verified upon investigation. If presuppositional apologetics are accepted, an implication is the invalidation of empirical methods, which is absurd. This is similar to the issue of whether the Bible produces logical contradictions; in Clarkian presuppositionalism, this is regarded as being a genuine problem.
Asserting Christianity is the only coherent view
Some apologists assert that "The Christian worldview alone adequately explains and accounts for the laws of logic."  Even if an apologist refutes the specific world view of their debate opponent, they do not attempt to justify their assertion that all other world views are inadequate. Therefore, this is an unsupported premise.
Tu quoque justification
Presuppositional apologetics has criticised atheists for using presuppositions.
- "Because your presuppositions will not allow you to examine without bias the evidence that I present to you for God's existence. [...] Your presupposition is that there is no God; therefore, no matter what I might present to you to show His existence, you must interpret it in a manner consistent with your presupposition: namely, that there is no God. "
Since atheist or perhaps everyone allegedly uses presuppositions, this supposedly justifies presuppositional apologetics. However, this is fallacious because the "presuppositions of atheists" are not relevant to the question of the existence of God. This is a tu quoque argument.
It is also a straw man argument since some atheists allow the possibility of their mind being changed by evidence. Arguably, many atheists "presuppose" skepticism and avoidance of dogmatism. These beliefs can themselves be subjected to skeptical examination. However, skepticism does not preclude belief in God.
It is also false to draw an analogy between skeptical presuppositions and religious presuppositions. Scepticism attempts to minimise assumptions while presuppositionalist believers assume quite a bit! This analogy is similar to the claim that religion is another way of knowing i.e. all belief systems are equally valid. An example of a faulty analogy:
- "Arguments for religions and philosophical systems are arguments for world views. A world view is a general account of all reality, an understanding of the most basic features of the universe. All arguments for the truth of world views (whether religious, philosophical, political, scientific or whatever) must presuppose standards of rationality consistent with those world views. All such arguments, therefore, are circular in a way similar to ours. "
If this conclusion was true, it would only imply that any such "world view" cannot be logically justified and not that presuppositional apologetics is justified. It is possible to live and provisionally believe things without any grand "world view", such as with existentialism or living without any knowledge of philosophy (naive realism).
List of presuppositional theologians
Notable proponents of presuppositional apologetics include:
- Cornelius Van Til
- Gordon Clark
- Greg Bahnsen
- John Frame
- Rousas John Rushdoony
- Francis Schaeffer
- Douglas Wilson
- Sye Ten Bruggencate
- ↑ John Frame, Five Views on Apologetics, 2010
- ↑ 
- ↑ Theopedia, Presuppositional apologetics, retrieved 4th July 2014
- ↑ 4.0 4.1 Glenn Hendrickson, Essay: Christianity Explains Logic, April 27, 2010
- ↑ Presuppositional Apologetics Destroyed
- ↑ Karen S, Yes, Another Pre-Sup Counter-Script New and Improved!, February 27, 2014
- ↑ Steve Shives, Five Stupid Things About Presuppositional Apologetics
- ↑ -Sigh- Oh Sye - Can you be Wrong About Everything you Claim to Know?
- ↑ The Refining Reason Debate, May 31st
- ↑ 
- ↑