What is the theme in Foundation and Earth by Isaac Asimov?

Pride is a theme in this book. Trevize is entrusted with the fate of the human race and it is left to him to decide whether the race will continue as individuals or to merge with a single consciousness - Gaia. There's little doubt that he should feel the weight of responsibility for that decision, but he also admits to feeling at least some measure or pride. The Gaians have complete trust in him and from the beginning say that they won't interfere with his decision-making process, though in theory they could sway his mind to their way of thinking.