The purpose of this book is to invite the reader to think. The truth can be communicated to a person in many different ways; it can be shown by the use of details, pieces of evidence and by using logic. Yet, if a person does not think over this truth on his own, sincerely and honestly with the purpose of comprehending the truth, all these efforts are useless. For this reason, when the messengers of Allah communicated the message to their people, they told them the truth clearly and then invited them to think.
A person who reflects, grasps the secrets of Allah's creation, the truth of the life of this world, the existence of Hell and Paradise, and the inner truth of matters. He obtains a deeper understanding of the importance of being a person with whom Allah is pleased, and so he lives by the religion as is its due, recognizes Allah's attributes in everything he sees, and begins to think not according to what the majority of people demand but as Allah commands. As a result, he takes pleasure from beauty much more than others do, and does not suffer distress from baseless misapprehensions and worldly greed.
These are only a few of the beautiful things a person who thinks will gain in the world. The gain in the Hereafter of someone who always finds the truth by thinking, is the love, approval, mercy and the Paradise of Allah. On the other hand, a day is near when those who today avoid seeing the truth by thinking will come to think, and moreover think deeply and meditate and see the truth clearly. Yet their thinking on that day will not be of any use to them but will make them suffer grief. Allah says in the Qur'an when these people will reflect: When the Great Calamity comes: that Day man will remember what he has striven for and the Blazing Fire will be displayed for all who can see. (Surat an-Nazi'at: 34-36)
Inviting people, who suppose that they can escape from their responsibilities by not thinking, to think so that they may reflect upon the end that will befall them and return to Allah's religion is an act of worship for believers. Yet, ultimately, as Allah states in the Qur'an:
… Anyone who will, may pay heed. (Surat al-Muddaththir: 55)