Full text article. Also available at http://sciencefront.org/ojs/index.php/jfap/article/view/150For three centuries Newtonian mechanics had been firmly established as a valid theory for the understanding of physical reality; if one understands the laws of physics, then one understands the whole universe. Classical physicists had contented themselves with the search for regularities in measurements and in the physical world. Irregularities were regarded as noises that interfered with the deterministic picture of physical reality. However, from 1900s onwards with the quantum hypothesis, physicists had begun to recognize that the physics of Newton and Maxwell were inadequate for the understanding of all of the physical reality. For example, the interaction of radiation with matter could not be explained from classical physics. This dilemma led to the discovery of quantum mechanics. In this article we explore the challenges that students face in understanding quantum mechanics that arises from paradigm shift in the mode of reasoning about the physical world. The description of physical reality in general and quantum reality in particular requires that we shift our mode of reasoning from classical Boolean logic to quantum non Boolean logic.