The correct answer is number 4) Thinkers began to observe and deduce their own ideas through reasoning.
In the 16th century, the thing that changed in the study of philosophy was that Thinkers began to observe and deduce their own ideas through reasoning.
We are referring to the period in history called the Scientific Revolution, where thinkers, philosophers, and scientist started to use the reason over the old beliefs and religious doctrines. Under this new circumstance, philosophers used reason and critical thinking to carefully observe the phenomena of the study, and many started to use logic and mathematics to support their ideas.
