Final answer:
d. Pythagoras. Pythagoras is the philosopher who set the stage for understanding human behavior and experience as related to internal processes and natural causes, as well as for his theorem regarding the sides of a right triangle.
Step-by-step explanation:
In the sixth century BCE, the philosopher Pythagoras set the stage for understanding human behavior and experience as related to internal processes and natural causes. He is also known for his theorem regarding the sides of a right triangle. The Pythagorean theorem states that in a right-angled triangle, the square of the length of the hypotenuse is equal to the sum of the squares of the other two sides. This theorem is widely used in geometry and has practical applications in various fields, such as construction and navigation.