This book consists of the following two philosophers:

- Anaximander: Anaximander is best known for his revolutionary ideas about the cosmos. He proposed that the universe originated from the apeiron, an indefinite or boundless substance, which he believed was the source of all things. This concept marked a significant departure from the mythological explanations of the cosmos prevalent in his time, suggesting instead a naturalistic origin of the universe. His cosmological model, which included the idea of a cylindrical Earth suspended in space, demonstrated a sophisticated understanding of celestial mechanics for his era.

- Thales: In addition to his contributions to philosophy, Thales was also a mathematician and astronomer, and his influence in these fields is considerable. He is credited with being the first to predict a solar eclipse, using his understanding of the stars and celestial movements. His work in geometry is equally important—he is famously known for Thales' Theorem, which laid the groundwork for the development of geometry. This theorem states that if two points are on a circle, and a line is drawn through them, then the center of that line will always lie on a straight line through the center of the circle. This geometric insight shows his ability to understand and systematize mathematical concepts that were previously unexamined.