Argument from divine sense
The argument from divine sense, or sensus divinitatis (SD) holds that belief in God can be considered properly basic, requiring no external justification such as physical evidence. The consequence is that no physical evidence would be necessary to demonstrate religion, if religion is true. On it's own, sensus divinitatis is not an argument for the existence of God. It is sometimes used to argue that atheists know there is a God.
The argument can be traced back to the early church but was largely developed by John Calvin.  It is an attempt to justify reformed epistemology. It has seen resistance from both believers and non-believers, though for different reasons. The argument eliminates any need for traditional apologetics that attempt to offer rational defences of faith and belief in God. It also eliminates traditional views of faith, encouraging a relativist position akin to "God is real for me, and that's all that matters." Additionally, theists and non-theists point out that even if the argument were sound, it cannot justify any particular God or concept of God beyond what the individual claims to experience.
- "There are certain sources of belief, we taken them as "basic" and they do not require further evidential justification, such as sense-perception, memory, intuition, etc. It may be, if Christianity is true, there is another faculty, that Aquinas called sensus divinitatis. This faculty, like memory, like intuition, like sense-perception, delivers beliefs about God. If Christianity is true, this faculty is reliable and we do not require further evidence. Therefore, we do not require physical evidence, if Christianity is true. "
The argument is very similar to the claim that religion is another way of knowing.
One formulation of the basic argument from divine sense (using Christianity as an example):
- Humans have faculties that provide the individual person with basic or foundational beliefs that do not require further justification.
- If Christianity is true, it is very probable that humans are endowed with a cognitive faculty in addition to memory, perception, etc. which we can call the sensus divinitatis.
- If humans have a sensus divinitatis, then Christian belief can be foundational.
- If Christianity is true, (very probably) Christian belief can be justified, without independent evidence.
The term sensus divinitatis may be an attempt at obfuscation by making the concept sound far more significant than it is. It certainly sounds important but, in reality, it isn't anything more than a "god detector". Without intending to be overly polemic, the argument could also be rephrased as:
- "If God exists, then he implanted a God detector in each of us."
Alvin Plantinga claims that that everyone has a sensus divinitatis, but that sin interferes with this sense.  He uses a slightly different conception of sensus divinitatis than John Calvin. According to Plantinga, it is the:
- "many sided disposition to accept belief in God (or propositions that immediately and obviously entail the existence of God) in a variety of circumstances"
- Main Article: Foundationalism
- foundational beliefs (also called basic or properly basic), which are accepted axiomatically and require no external justification;
- all other beliefs, which are derived from foundational beliefs.
Foundationalism is not universally accepted, and competing epistemological philosophies exist which include objections to the premise of properly basic beliefs.
Acceptance of divine sense
Those who accept this reformed epistemology assert that Christian teachings necessarily support the existence of SD and that this assertion can only be challenged on exegetical grounds. They hold that a number of passages in the Bible imply or affirm the notion that God has given everyone a mechanism for knowing and understanding his nature.
This assertion isn't accepted, to the same degree, by all Christians and additional passages from the Bible along with testimonials from believers clearly claim that God can, and does, interact with the physical world in empirically observable ways, not the least of which is the Christian doctrine that God came to earth in a physical form to deliver the most important message in Christendom. This sort of physical interaction would not be necessary if a properly basic SD existed.
William Lane Craig, who uses some of the same arguments generally as Plantinga does, has been hesitant to endorse the idea of an innate "sense", and prefers the idea that there is instead an externally controlled "experience" that the believer has in encountering God. An obvious problem here is that it's not possible to objectively settle this question, especially when Christians who in theory believe similar things, find that they can't agree on the nature of the experience that they supposedly share. If the "sense" really is just a type of personal experience, then we're really talking about a different sort of argument, which has its own problems.
Sensus divinitatis is real
- "That there exists in the human minds and indeed by natural instinct, some sense of Deity, we hold to be beyond dispute, since God himself, to prevent any man from pretending ignorance, has endued all men with some idea of his Godhead, the memory of which he constantly renews and occasionally enlarges, that all to a man being aware that there is a God, and that he is their Maker, may be condemned by their own conscience when they neither worship him nor consecrate their lives to his service."
- "All men of sound judgment will therefore hold, that a sense of Deity is indelibly engraven on the human heart. "
This still follows the basic form of the argument: (1) God exists, (2) God "has endued all men with some idea of his Godhead", (3) we know God exists.
Begging the question
- Main Article: Begging the question
If used to argue for the existence of God, the conclusion that God exists is also contained in a premise of the argument, making it circular:
- If Christianity is true, divine sense exists.
- If divine sense exists, Christianity is true.
- "It is that it rests on the fallacy of informal logic known as petitio principii. Plantinga wishes to claim that we can know there is a deity because the deity has provided us with a cognitive modality, which Plantinga calls “a sensus divinitatis,” or sense of the divine, by which we detect its existence. So, we know there is a god because that god arranges matters so that we know there is a god. The circularity is perfect, and perfectly fallacious. "
Arguably, Plantinga does not even attempt to show that sensus divinitatis proves God.
Weak conclusion based on unsubstantiated premises
The existence of several conditionals in the argument render it ineffective - "if Christianity is true", "very probable", "if humans have a sensus divinitatis". There is no evidence that sensus divinitatis exists. John Calvin's argument that "everyone believes in God" is a hasty generalization and a majority argument.
Even if it were valid and sound, the most it could ever prove is the possibility that the state of affairs it presents were true - and that possibility wouldn't be exclusive to any particular religion. Removing the conditionals removes this argument from the realm of the hypothetical and places the believer back in the position of having to defend the truth of the claims they make - and that's the real purpose of this argument: it is an attempt to avoid the burden of proof.
Divine sense is assumed to be basic
A premise of the argument states that SD can be considered properly basic. Instead of acting as an argument supporting reformed epistemology, it merely assumes that position is true and moves on.
For foundationalists, the justification for considering any belief properly basic is, on the one hand, avoidance of an infinite regress. Belief B is justified by B', which is justified by B", etc. To avoid the regression, one simply accepts that some beliefs do not require justification. Those who agreed with this principle also understood that dogmatically declaring beliefs as basic is no solution, as anyone could declare any belief basic and avoid the need to justify it - in other words, something can't be properly basic just because we claim it to be so. One major objection, from Christians and non-Christians, alike, is that this argument attempts to do exactly that.
For modern foundationalists, properly basic beliefs aren't dogmatically asserted, they have an inherent justification which places them in the position of requiring no further justification. The defining characteristics which render a belief properly basic are consistency and reliability - to the point that questioning the justification of those beliefs is nonsensical and counter-productive. While sensory data was considered properly basic among classic foundationalists, modern foundationalists reject this notion - because our senses can be unreliable and aren't above question. Sensory data can be viewed as "near" basic, or justified by the basic notion that the information our brains process is generally reliable, but subject to corroboration.
No specific religion or theology is supported
- Main Article: Which God?
Yet another objection to this argument is that it doesn't create an argument that necessarily supports only Christianity. Consider the argument again, with another religion or belief replacing Christianity along with it's claim of something akin to sensus divinitatis. The conclusion will work for any claim which includes a method of self-confirmation.
If the basis for asserting the existence of SD is a specific interpretation of Christian scripture, then alternate interpretations render the assertion suspect and the first premise should read:
- "If this particular interpretation of Christian scriptures is correct, then humans have a sensus divinitatis"
Apologists would claim that this is why the premise says "very probable" instead of "necessary" but there's no clear way to determine which interpretation can be considered "very probably" correct, if any can. In truth, the first premise is a personal opinion which, after removing the conditionals should read:
- "My interpretation of Christian scriptures supports the existence of a sensus divinitatis"
Many different religions exist
This raises questions about the reliability of claims attributed to a sensus divinitatis. If we operate under the assumption that SD exists:
- How do we explain the lack of such claims from the non-religious?
- How do we explain contradictions between scientific knowledge and claims of divinely revealed knowledge?
- How do we explain the many inconsistent and/or contradictory claims about god/God/gods made by members of various religions - including members who profess to be of the same religion?
There are more than 1000 denominations within Christianity and there have been many other religions and sects which claim to worship the same God, rely on many of the same scriptures and have claimed rough equivalents of SD. To even the most casual observer, this situation should call the reliability of claims regarding SD into question.
"There are more idols than realities in the world: that is my "evil eye" upon this world; that is also my "evil ear.""
Also, beliefs that are created by a sensus divinitatis cannot be distinguished from beliefs that are the result of delusion or mental illness.
Assuming the characteristics of God
The argument assumes that God would want people to know he existed but this has not been properly established. Also, it is simply assumed that divine sense is reliable and God is not a trickster. Given humans are often wrong in their beliefs, we would not expect sensus divinitatis to be any different. How can sensus divinitatis caused by either God or Satan be distinguished?
A predisposition to believe in God proves nothing
Humans have cognitive biases, which sometimes leads use to perceive things that are not there and believe things that do not reflect reality. A predisposition to believe in God may be nothing more than our limited brains struggling to comprehend a godless universe. Our tendency to believe something is true does not make it true; in fact research into cognitive biases shows our beliefs are often unreliable! There is evidence that the human tendency to believe in divine agents is an evolutionary adaptation.
Contradicted by scripture
Even the Bible contradicts the simplest view, that everyone knows about God deep down. Psalms 14:1 says, "The fool hath said in his heart, There is no God." It seems hard to argue that anyone could say "in his heart" that there is no God while not believing that there is no God. Therefore, the Bible acknowledges that at least some atheists exist (and they are "fools" by Biblical definition).
Reversing the argument
The argument cuts both ways:
- If Christianity is true, everyone would have sensus divinitatis
- Many or all people have no sensus divinitatis
- Therefore Christianity is false
Accounting for different religions
In response to criticism that many religions exist, apologists sometimes claim that humans were originally created with a perfect sensus divinitatis, but after man sinned by eating from the tree of knowledge, part of his punishment was a separation from God which rendered this divine sense unreliable.
"Like any cognitive process, however, the sensus divinitatis can malfunction; as a result of sin, it has indeed been damage"
- — Alvin Plantinga
They claim that this broken SD will be repaired, for "true" believers, by God. Some of those who would use this argument would re-write the relevant premise to read:
- "If humans have a properly working SD, then Christian belief can be foundational"
This ad hoc explanation completely undermines the argument. It creates a logical disconnect between two premises. One premise refers to simply "SD" while the other premise adds the qualifier "properly working". This invalidates the argument and the conclusion cannot be reached without also changing the next premise to include the qualifier. If we modify both premises to reconnect the argument, the validity is restored, but the dilemma (how do you explain inconsistencies?) returns and the revised argument has new problems:
- If Christianity is true, it is very probably that humans are endowed with a properly working SD
- If humans have a properly working SD, then Christian belief can be foundational
- If Christianity is true, very probably Christian belief can be justified without independent evidence
The new problem is that we've added yet another conditional to the argument - properly working - which, without additional information, renders the argument even more ineffective. Modifying these premises demonstrates the fundamental flaws inherent in making claims of divine revelation:
- How do you distinguish SD from psychosis, delusion or wishful thinking?
- How do you know whether or not your SD is working properly?
- How do you know that your SD isn't being intentionally manipulated by Satan?
- Wouldn't a truly evil and near-god-like being prefer to have you believe you're understanding God when you're really understanding him?
The unreliable and often contradictory nature of claims attributed to SD clearly ensure that it shouldn't be considered properly basic. This is only exacerbated by ad hoc explanations to explain the unreliable nature of these claims which seem to be desperate attempts to avoid the obvious conclusion - there is no sensus divinitatis.
- ↑ 1.0 1.1 Prayson Daniel, Sensus Divinitatis, November 5, 2013
- ↑ Paraphrased from Atheist Experience, #455, from 41:23-54:30.
- ↑ 3.0 3.1 Plantinga, Warranted Christian Belief, p. 214. 
- ↑ John Calvin, Institutes of the Christian Religion, 1536
- ↑ 5.0 5.1