When you believe that ‘you know’ while you do not, you deprive yourself of the most significant source of intellectual development, the spirit of enquiry. Almost all the sciences have been the product of this spirit. First, the spirit of enquiry has to be fostered; only then will it lead to research and discoveries. In the famous story alluded to Isaac Newton, an apple that fell on him led him to wonder and contemplate the mysterious universe. Soon he understood that the very same force that made the apple fall toward the ground also keeps the moon from falling toward the earth and the earth from falling toward the sun: gravity People do not know, but they are convinced that they know. This tendency is the greatest hindrance to intellectual development.