When religion stops being about researching the Truth and becomes a mere set of customs (or habits) that we inherit from our forefathers, that’s when it becomes vulnerable to corruption. Mistakes and misunderstandings are made by some of our ancestors, but they go unnoticed because we never dare to question or challenge them.
Over time, as these mistakes and misunderstandings pile up, the religion changes from the pure system that God revealed to His messengers to one of many corrupted versions of it.
The Quran emphasizes the importance of independent/critical thinking (6:116, 17:36, 33:67). It also discourages us from blindly accepting whatever beliefs we inherited (5:104, 7:28)
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Many believe that the Islamic Calendar is lunar. But how could it be when most of its months are named after seasonal events? Thankfully, the Quran contains a few hidden miracles hinting to the true Islamic Calendar. (38:29)
“It is impossible for a man to learn what he thinks he already knows” – Epictetus