A study of the Quran shows that the Quranic teachings are based on realistic approach. When we use the term “realistic approach” to describe a way of thinking, it always means, thinking that is in accordance with reality. One with such a bent of mind will be scientific in all his dealings in the world. His thinking will be totally in accordance with external realities. According to the Quran, there are two kinds of thinking—sincere thinking and insincere thinking or double-standard thinking. The scientific approach is characteristic of a sincere thinker. A sincere thinker cannot envision an approach which is not based on realism. He bases his life on sound and true foundations. On the contrary, it is the insincere thinker who has no principles or scruples. His approach is based on opportunism and he changes his point of view and way of thinking to serve his own interests. That is why there is not even a grain of the scientific approach in him. His thoughts and deeds are totally unpredictable.