Sin is not only a moral, social, and relational problem; it is an epistemological problem as well. While we often refer to actions which are contrary to God’s will as sins, Sin is greater than the some of these parts. Sin is the condition of the distortion of our entire being which manifests itself in our thinking, feeling, and acting. It is an individual and a corporate condition, manifesting itself not only in the actions of individuals, but of groups, societies, cultures. It is clear then that Sin affects our reasoning and hence our knowing. This is often referred to as the noetic effects of sin.
In his article ‘How Sin Affects Scholarship: A New Model,’ Stephen K. Moroney presents and offers a critique of two models of the noetic effects of sin represented in the teachings of Abraham Kuyper and Emil Brunner, followed by a constructive proposal of his own.
While Kuyper and Brunner present two different models, they share a crucial similarity. Both Kuyper and Brunner posited (in somewhat different ways) that the noetic effects of sin are felt most when it comes to matters of theology and ethics, and least (if at all) when it comes to matters of observation and logic (e.g. natural sciences, mathematics). The dependence of Christians on Revelation/Scripture for the former sets us radically apart from all others, whose efforts to establish truth in such matters will necessarily rely on self-sufficient reason and come to err. They both tie sin to reason employed apart from revelation/scripture. As Moroney observes regarding Brunner, ‘Nowhere does he speak of the noetic effects of sin in believer’s thinking. Brunner’s argument is always from the noetic effects of sin to the distinctives of Christian thinking.’ (441) Both Brunner and Kuyper focus on the object of study and ignore the subject doing the studying, apart from what they consider to be the determinative factor; whether the subject is a Christian or not (440). Unfortunately this is a serious shortcoming, reminding me of the way in which “reason” is sometimes set in opposition to “faith” or “revelation.”
In my own words, in these models Sin does not affect the process of reasoning at all, rather, the state of the world as fallen means that we cannot know the truth in matters of theology and ethics apart from God’s revelation. Therefore those outside of Christ will always be “blind” in such matters. It matters then a good deal what we mean by the term “Sin” in this discussion.
For his constructive proposal Moroney uses sin to refer both to acts (whether mental, emotional, or physical) that are contrary to Gods will, and the disposition to carry these out. (442, fn.49)
While Moroney agrees with Kuyper and Bruner that sin ‘tends to disturb human thinking about some matters more than other,’ (442; this is represented in “the object of knowledge” column from less (bottom) to more (top)) the noetic effects of sin include the distortion of the process of our thinking, not simply in terms of the sources we employ, but in terms of the influences on our judgments.
Because the noetic effects of sin involves ‘the complex interplay of multiple factors’ as indicated in the diagram, the noetic effects of sin vary from person to person, and it is not possible to ‘forecast exactly’ how sin will distort someone’s thinking. (447) I think this point is very important. When it comes to biblical interpretation, we do not always come to the wrong conclusions because we wish to believe that the text says something, even where the more controversial issues are involved. And we should not assume to or judge that others are doing so lightly. According to Moroney knowledge (however comprehensive) of the factors that shape and influence any particular ‘knowing subject’ is not necessarily enough to determine how sin is affecting someone’s reasoning. Sometimes it is, and we may claim that is very clearly so. But we need to recognize the complexity before rushing to conclusions.
What this should lead us to first and foremost is to a heightened self-awareness and a chastened view of our own success in the pursuit of truth:
‘The reality that sin distorts our thinking reminds us not only of our need to be self-critical and open to others’ corrections but also of our need to humility. If we take the noetic effects of sin seriously, then we are faced with the humbling prospect that this side of heaven some of our beliefs, in particular our beliefs about God… will be erroneous.’ (449)
So it should be clear that the flaws or errors in our thinking (its processes and results) are not always the effect of sin. We all have a capacity to know, to understand, but most of the time this requires effort and work. Understanding and misunderstanding are simply part and parcel of the way in which our thinking/inquiring is designed to function, and I do not think that this is the result of a “fall.” I think it is simply how God has chosen to create us. It is Sin that we introduced into the world which complicates the whole Endeavour.
 S.K. Moroney ‘How Sin Affects Scholarship: A New Model,’ Christian Scholar’s Review XXVIII:3 (Spring 1999): 432-451.
 “Reason” is not itself a source of knowledge to be set against or alongside of revelation. Rather reason is employed in the persuit of knowledge, whether the source of this knowledge has made it clear (revelation) or whether it needs to be generated through inquiry into that of which knowledge is sought. I realise that the distinction is often made between knowledge gained through revelation and knowledge gained through reason, but here I think the latter term is not entirely appropriate and confuses matters.
The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge.
What if any, is the difference between knowing something and believing something? This itself is a massive philosophical question and I only here want to reflect in general terms about one way in which we use such language in general conversation. 
Consider general conversation. We may ask someone what they believe about a topic or an issue—perhaps God or climate change—and we may even ask them why they believe so, but we do not generally ask people what they know about such things. Why is this? When we use the language of belief in such a situation we are implicitly acknowledging a plurality of perspectives on the issue. To ask someone what they know about God would be to suggest that one wants to take on board what they say as fact. For example, it is typical to ask professionals and experts for their knowledge in an area, but we may even ask experts what they believe if we think we might currently hold a different position.
From the other side of the conversation it would be out-of-place to answer a question about ones beliefs by stating what one knows; this can create discomfort because knowledge carries with it a universal claim. We speak about knowledge in the areas of science for example, of matters which we can access through our senses and which we can reach assured results. Belief however does not hold a universal claim. We often use the language when referring to matters which are beyond the reach of our senses, for matters which we cannot reach assured conclusions on. Such things are often placed in the category of personal preference because we cannot truly know the facts.
So the language of belief in general conversation allows for a diversity of perspectives and stops short of making a universal or factual claim upon others. The language of knowledge on the other hand does make universal claims and we do not use it when asking people about controversial matters.
But in using the language of belief are we are in risk of inadvertently nodding our head to two features of contemporary culture: pluralism and uncertainty. In common conversation about God or religion the language of belief can make way for the acknowledgement of a plurality of perspectives, and this is helpful. But if we are not careful our partners in conversation may get the impression that we consider our positions to be beliefs because they fall short of an adequate basis that makes for knowledge. We do not want people to get the idea that we only believe but do not claim to know, either because we lack certainty or reasonable and intelligent grounds for them, that there is no way of us truly knowing, or that they reflect mere personal preference as that which suites us.
Assuming you don’t fall into any of these categories, this is a bad impression we need to avoid! So lets be consious of the language which we use when we speak with others.
 I am not addressing how such language may function in the Bible, theology, or academic discourse, only in general/common/informal/everyday conversation.
 Consider a television or radio interview. If the interviewer intends to present the interviewee as an authority on the topic to enlighten the audience, then they will often frame the questions in terms of knowledge rather than belief.
 This is simply how the language is often used, regardless of the inadequacies of the epistemological assumptions that under gird it.