What struck me about Letters to a Young Scientist was his sincere and honest plea for young students to become scientists. Had I heard his message 40 years ago I would have become a biologist. How the survival of the world depends on society producing individuals who know enough about the biosphere to show us how to halt our destruction of it.
This advice followed directly from the former book, The Social Conquest of Earth. Here he asks the great questions: Where do we come from? What are we? Where are we going? And without spoiling his conclusions the arts and humanities still have something to say about this, but only when informed deeply by modern science. We have as a species conquered earth, but we need young scientists who understand the sciences to truly be its caretakers.