In the dialogue Theaetetus, Socrates notes that a sense of wonder is the mark of the philosopher. What Plato means by wonder is evident from the passage and from his use of the term elsewhere as a reference to curiosity, to questioning, to seeking an answer to the questions raised by life, and so on. The comment is made by Socrates to Theaetetus in the midst of their discussion:
I see, my dear Theaetetus, that Theodorus had a true insight into your nature when he said that you were a philosopher, for wonder is the feeling of a philosopher, and philosophy begins in wonder. He was not a bad genealogist who said that Iris (the messenger of heaven) is the child of Thaumas (wonder) (Library of the Future Screen 32:158).
An examination of this passage and Plato's writings will show that philosophy and wonder are connected, with wonder being a necessary condition for the philosopher.
Plato uses the word "wonder" often in the dialogues, but generally he does not use it in the same direct sense he does in this dialogue. Usually he is expressing a sense of wonder at various statements or ideas rather than commenting on the idea of or importance of wonder itself. Yet this very repetition of the phrase shows that the philosopher is brought to a state of wonder by issue he does not fully understand, and the act of wondering becomes the starting point for further discussion and examination.
The subject matter of the Theaetetus is significant in this discussion, for it involves a reexamination of some issue raised in earlier dialogues, specifically questions of epistemology that had been argued in the middle dialogues. In effect, Socrates is challenging some of his own earlier determinations. The claim had been made earlier that perceptible things are not stable and that this means there can be no knowledge of them. Instead, only the Forms can be known, for they are stable and are also not perceptible. In Theaetetus, however,...