Humans want to be sure about what they believe in, but those who give their will to another’s hands can never get rid of doubts. Doubts are infections in the heart and the heart needs a constant treatment of Faith conducted by reasoning. Humans are expected to clear up doubts in their hearts with sound arguments.
Philosophy was long regarded as the sole method of thought that would explain phenomena, be it imaginary, concrete, celestial, or terrestrial. Aristotle was a biologist, if we look at his work from today's perspective. He was mainly interested in the species that scattered all over the places. His concern was to collect as many different animals and plants as possible, so that he would have been able to talk about them with greater certainty. However, he was also a strong advocate of categorization and in order to categorize what he had collected, he needed to contemplate on what to put in this or that category or on what makes two things different. This contemplation made him a philosopher, as we understand it today.