* Plato: He emphasized reason and logic as the path to knowledge and understanding the Forms, which are perfect, eternal, and unchanging essences of things. His dialogues are full of reasoned arguments and explorations of philosophical concepts.
* Aristotle: While differing from Plato in some key respects, Aristotle is also considered a cornerstone of Greek rationalism. He developed formal logic, emphasized empirical observation alongside reason, and systematically categorized and analyzed a vast range of knowledge.
* Socrates: While leaving no written works, Socrates, through Plato's accounts, is seen as a pioneer of rational inquiry. His method of questioning (the Socratic method) aimed to expose contradictions in beliefs and guide people towards rational understanding.
While others contributed, these three are generally considered the most significant proponents of Greek rationalism. It's important to note that "rationalism" in this context isn't precisely the same as its later, more formal philosophical definitions, but encompasses the emphasis on reason and logic in understanding the world.