1) Reliance on Conjecture Instead of Sure Knowledge
The Holy Qur'an says: "Most people are such that if you follow them they will lead you away from the right path, because they rely on conjecture only." (Surah al-An'am, 6:116)
The Holy Qur'an strictly forbids following a conjecture. It says: "Do not follow that of which you have no knowledge. Indeed the ear, the eye, and the heart each will be questioned." (Surah Bani Isra'il, 17:36)
The philosophers admit that dubious knowledge is the main cause of mistakes. Many centuries after the revelation of the Holy Qur'an, Descartes declared this to be the first principle of his logic. He said: "I do not consider anything to be a reality unless it becomes obvious to me. I avoid haste, association of ideas and predisposition; and accept only that which is so clear and distinct that there can be no doubt about it"