Intuitively, it seems like "why?" questions can be asked without end – that ideas cannot stand alone without deeper reasons. But in fact, there are truths so foundational that the question "why?" does not apply. These truths are not contingent on other premises; they are necessary. In fact, these truths are so fundamental, that every other idea presupposes them. They rest at the bottom of every worldview, whether explicit or implicit. They are certain, absolute, and objective. Without them, one cannot even have coherent thoughts.
This is one of the claims of the book. That some truths are absolute.
