What metaphors are used in A Brief History of Time by Stephen Hawking?

Hawking often revisits ideas along his thinking trip and expands on them, fleshing out what had been served in skeletal form. Apparent contradictions fall away as the reader comes to understand that different theories give rise to different possibilities. The universe can be thought of in several ways. Physics has no one answer to it all, and revisiting different theories helps to keep this perspective. To use another metaphor, Hawking moulds the reader's concepts of the universe, but desires that they should remain elastic upon finishing the book, not set in bronze. The framework of the book contains this elasticity, clay within a cage.