Question

According to the First Doctor, questions, indicative of curiosity, were "the beginning of wisdom, of knowledge [and] of understanding". When a species began asking questions, no matter what prompted their inquiry, they arrived at a new frontier for their society. This was an evolution of sorts, the Doctor suggested. Though the nature of the questions themselves varied according to circumstances, "no matter how trivial they might seem [...] they have an unsettling tendency to lead to further questions".

This exponential rise in curiosity, beginning in this form across "all species", commonly culminated in an exploration of grand ideas and profound thoughts, which the Doctor favoured calling the "great unknown". (AUDIO: The Invention of Death)

The oldest question in the universe was "Doctor who?" (TV: The Wedding of River Song) According to the Fifth Doctor, the "second-oldest question" was "Why did the chicken cross the road?" (AUDIO: The Second Oldest Question)