So far we have only dealt with the sin of disbelief in God and with the general framework of the basis of knowledge in terms of good and bad thinking. The sin of disbelief in God is essentially the product of rejecting the effort to do what is morally right. This applies to general actions and in particular to exercising good thinking as it would inevitably lead to belief in God as the ultimate explanation of reality in both the senses of the question "Why?" i.e. "So What?" and "How?".
What makes good thinking is at the core a question of sincerity and when one rejects good thinking one is essentially undergoing self-deception of one form or another. It is not necessary to be intelligent to have good thinking - though good thinking may well lead to greater intelligence. What matters is sincerity; wanting to do what is morally right. Someone who practices good thinking is essentially someone with a clear conscience. Insincerity and self-deception are core to the concept in Islam of the disbeliever. The word used for disbeliever in Islam is "kafir" and has the literal meaning of someone who covers up. I could go into many quotes from the Qur'an of the nature of kafir but I'll leave that to the reader to discover for themselves. What I will quote here is the essentials of belief which apply to all people:
...any who believe in Allah and the Last Day, and work righteousness, shall have their reward with their Lord; on them shall be no fear, nor shall they grieve.
Surah 2 Verse 62
This brings in the subject of the last day or judgement day. The need for judgement day can easily be understood once moral teachings are recognised as having real meaning. Moral laws are like physical laws. If I am in a state of self-deception as to the laws of physics I might decide to punch my hand into a concrete wall. It would hurt me a lot but that is the natural law. It is the same way with morals. If I refuse to acknowledge that which is evident to me and I do something to spite it, I am only going to cause harm to myself in the long run. If I deliberately do wrong it is no different from me punching my fist into the concrete I should expect it to hurt and I have no excuse. The difference with morals is that the consequences are sometimes well into the future whereas punching concrete has an immediate consequence.
However, all this only gets us so far. Morals relate to how we should act over such issues as the use of drugs, sexual morals, use of violence etc and this concerns much more that the general principles we have been discussing so far. Morals can be learned to some degree through life's experiences, cultural traditions can get passed on through the generations and sciences can come to some sort of conclusions. However, morals are often considered to be different from descriptions of the physical reality around us and indeed they are. This is the Is / Ought problem again. In the earlier pages I have in a way partially bridged this divide by tackling the very categorisation: we only have 'Is statements' because we keep to a foundation of good thinking which results in our knowledge. That said, we still don't have a firm basis for deriving morals; we have really only asserted the integral and essential nature of moral intent in the way we observe and think about reality in general. How can we approach, for example, the question of the morality of drinking alcohol? To judge an act to be morally right or wrong, we need to know the ultimate consequences of its effects. This we are in principle not able to do, because such knowledge is beyond our ability to know. We can only know a few of the effects. Morals also are not subject to experimentation as are purely non-living phenomena. We cannot morally justify forcing people to behave in certain ways to see the effects. Indeed any forced behaviour cannot be moral because it is not freely chosen. The only real source of legitimate knowledge on this subject is history. History tells us that no culture has ever maintained morality over time without having a strong religious underpinning. This is because the only source of suitably qualified moral teachings is the ultimate cause and explanation of reality, who is therefore all-knowing and the one who knows the ultimate outcomes - Allah.
From this we see that revelation has been the source of moral guidance throughout history. The question that is critical though is to distinguish between genuine revelation and fake. How are we to know what is true revelation from Allah? To answer this I shall return to the concepts described before in the sin of disbelief. To really resolve the Is / Ought problem we use the principles of good thinking to analyse the evidence that some scripture claiming to be revelation actually is revelation. First we must consider what kind of evidence would demonstrate the truth of a revelation.