The Transcendental Argument for the Existence of God (TAG) is the argument that attempts to prove the existence of the Christian God by arguing that logic, morals, and science ultimately presuppose a supreme being and that the Christian God must therefore be the source of logic and morals.
A version was formulated by Immanuel Kant in his 1763 work The Only Possible Argument in Support of a Demonstration of the Existence of God, and most contemporary formulations of the transcendental argument have been developed within the framework of Christian presuppositional apologetics.
Transcendental arguments should not be confused with arguments for the existence of something transcendent. In other words, they are distinct from both arguments that appeal to a transcendent intuition or sense as evidence, and classical apologetics arguments that move from direct evidence to the existence of a transcendent thing.
They are also sometimes said to be distinct from standard deductive and inductive forms of reasoning, although this has been disputed, for instance by Anthony Genova and Graham Bird.
Medieval Ash'ari Islamic theologians formulated a type of transcendental argument based on the notion that morality, logic, etc. cannot be fully understood apart from revelation and thereby, belief in the Quran and the Islamic truth claims were necessary in order to interpret the external world. For al-Ashari and others, it does not make sense to argue against religion using a priori assumptions about morality or scientific probabilities when these can only be understood in light of divine revelation.
The TAG is a transcendental argument that attempts to prove that God is the precondition for logic, reason, or morality. The argument proceeds as follows:
Cornelius Van Til likewise wrote:
We must point out ... that univocal reasoning itself leads to self-contradiction, not only from a theistic point of view, but from a non-theistic point of view as well... It is this that we ought to mean when we say that we reason from the impossibility of the contrary. The contrary is impossible only if it is self-contradictory when operating on the basis of its own assumptions.— (A Survey of Christian Epistemology [Philadelphia: Presbyterian and Reformed, 1969], p. 204).
Therefore, the TAG differs from thomistic and evidentialist arguments, which posit the existence of God in order to avoid an infinite regress of causes or motions.
Some reject the validity of the argument pointing out various flaws, such as a category error involved in the first premise of the argument, namely that just because there is a statement that is universally true it will not make that statement a part of reality in itself.[disputed (for: Citation of Dubious Credibility) ] Another issue pointed out is that it is not needed to have a god to have logic or morality. In particular the existence of multiple logic systems with differing axioms such as non-classical logic as well as multiple radically different moral systems constitutes evidence against the idea that logic and morality are actually universals. Furthermore, the existence of theorems like Gödel's completeness theorem and the soundness theorems for classical logic provide justification for some logic systems like classical propositional logic without using any god hypotheses thus contradicting the first premise of the argument. It is worth noting however that Gödel also produced a classical propositional proof of god in Gödel's ontological proof. Finally, Internet Infidels co-founder Jeffery Jay Lowder has argued that TAG is fatally flawed for numerous reasons. First, Bahnsen failed to defend the necessity of Christian theism for the rational justification of the laws of logic, the laws of science, and the laws of morality. Second, Bahnsen conflated "atheism" with "materialism" and TAG is really an argument against materialism, not an argument for theism. Third, Bahnsen believed that the laws of logic, laws of science, and laws of morality were abstract objects, but Christian theism underdetermines the relationship between the Christian God and abstract objects. Some Christian philosophers, such as Peter van Inwagen, affirm heavyweight Platonism and the compatibility of Platonism and Christianity. But other Christian philosophers argue that Platonism is incompatible with divine aseity. William Lane Craig urges Christian philosophers to consider anti-realist theories of abstract objects.
But what about The Transcendental Argument for the Existence of God (TAG)--the argument that logic, science, and objective ethical standards presuppose the existence of God?