Knowledge is like money: to be of value it must circulate, and in circulating it can increase in quantity and, hopefully, in value.

One who returns to a place sees it with new eyes. Although the place may not have changed, the viewer inevitably has. For the first time things invisible before become suddenly visible.

If you wait for inspiration, you're not a writer, but a waiter.

Books are the perfect Time Machine. By the simple act of opening a book you can, in an instant, be travelling up a jungle river without once being bitten by mosquitoes, or you can almost die of thirst in the desert while holding a cold drink in your hand, or dine in the finest restaurants and never have to worry about paying the bill, or ride the wild country of our western frontier and never worry about losing your scalp to a raiding party.

Adventure is just a romantic name for trouble. It sounds swell when you write about it, but it's hell when you meet it face to face in a dark and lonely place.

... the mind must be prepared for knowledge as one prepares a field for planting, and a discovery made too soon is no better than a discovery not made at all.