The phrase "I know that I know nothing" is famously attributed to the ancient Greek philosopher Socrates. It comes from Plato's account in which Socrates expresses awareness of his own ignorance, stating that true wisdom begins with acknowledging what one does not know. This idea is foundational in Western philosophy and is often called the Socratic paradox.
Another notable related quote is "How can I know what I think until I see what I say?" attributed to E. M. Forster, which stresses the importance of expression in understanding one's own thoughts.
If the question is about "who said what can I know," the most relevant philosophical inquiry is that of Socrates regarding knowledge and ignorance, asking what we truly can know. Immanuel Kant also famously addressed the question "What can we know?" in his work "Critique of Pure Reason," which explores the limits and capacities of human knowledge.
Thus, the answer to "who said what can I know" connects primarily to Socrates' acknowledgement of ignorance and Kant's exploration of the boundaries of knowledge.
