The title of physicist Sean Carroll’s latest book, The Big Picture: On the Origins of Life, Meaning, and the Universe Itself, is proof of its ambition. This book wants to tie together, well, everything. That’s no surprise; many popular science books have wide scopes and aim to tie together disparate scientific information.

But The Big Picture is more philosophical than scientific, which is a bit of a departure for Dr. Carroll. Another of his books, From Eternity to Here: The Quest for the Ultimate Theory of Time, is equally ambitious but heavy on the science. That book was largely about examining and weighing various scientific possibilities. His new book takes a step back and asks how we should be thinking about these possibilities in the first place.

But don’t be discouraged if you prefer science over philosophy: Carroll seamlessly weaves the two together. The Big Picture lives up to its title. It starts at the Big Bang, explains how time works (drawing on ideas from Carroll's previous book), passes through chemistry, biology, computer science, evolution, abiogenesis (the study of how life on Earth started), quantum mechanics, and neuroscience, all before finally arriving at a discussion of how consciousness is possible.

But before exploring how philosophical and scientific questions often intersect, Carroll provides a framework for how to think about these questions. He introduces concepts such as Bayesian reasoning, and after taking readers through some early scientific history, he makes it clear that philosophy and science have long enjoyed a close relationship. Science, in many respects, is built on philosophical ideas about how we should weigh evidence.

Poetic naturalism

The book is also, in Carroll’s words, “an explication of, and argument for, naturalism.” Naturalism is a philosophy that argues there’s only the natural world and no supernatural—no psychics, no ghosts, and no God.

Science... is built on philosophical ideas about how we should weigh evidence.

But Carroll treats these notions and their believers respectfully. Instead of deriding them, he takes their claims seriously enough to explore them using the same principles he uses for everything else in the book. Carroll previously debated theologian William Lane Craig on the existence of God from a scientific perspective, so advocating naturalism isn’t new territory for him.

Carroll argues that the scientific view of the world is a consistent and powerful one and doesn’t need anything beyond the natural to function, even if pieces of our reality sometimes give the illusion of an outside, intelligent influence. He shows how evolution functions on its own, for example, without having to appeal to Intelligent Design and how chemicals can give rise to life in the early Earth despite the apparent improbability of that happening. None of that necessarily means there’s no God (though Carroll offers some points which might suggest that). But it does show the power and self-sufficiency of our best scientific understandings of the world.

The Big Picture argues for a specific brand of naturalism, which Carroll calls “Poetic naturalism.” “Poetic naturalism” is distinct from forms of naturalism that argue that things like human consciousness don’t actually exist. What exists, the latter argument goes, is atoms interacting with each other, and, from far away, they give the illusion of a person with wants and feelings. Poetic naturalism instead argues that consciousness is real, even though it’s made out of atoms.

Just because something is emergent (which means "arising from the collective behavior of the pieces that make it up") doesn’t mean that thing doesn’t exist. Cars are made of smaller things, but calling something a car is more useful than “that collection of metallic pieces sitting atop circular things made from rubber.” Carroll argues consciousness is real in the same way. He even takes the argument further by applying it to the question of free will.

Essentially, he argues, it’s not that either atoms exist or cars do. We just have two different sets of vocabulary for talking about the microscopic world and the macroscopic, human world we live in. Both are valid and true; they’re just true within two different domains of applicability. Both describe aspects of the same underlying reality.

The Big Picture

Throughout the book, Carroll dives into other hard-to-resolve problems: how could we tell the difference between a conscious robot and a robot that imitates consciousness really well? How do we know that my idea of ‘red’ is the same as yours? Are you still you if we slowly replace your neurons with mechanical "neuristors"—and if not, at what point do you stop being a person?

Carroll argues that the scientific view of the world... doesn’t need anything beyond the natural to function, even if pieces of our reality sometimes give the illusion of an outside, intelligent influence.

If all that brain stuff proves too much for you, don’t worry: the book also has plenty of zombies to remedy that.

In all his arguments, Carroll systematically examines possibilities and combines examples from disparate fields. He dives into difficult philosophical conundrums but isn’t afraid to come to a definite conclusion about them when he has logical justification for doing so. You may not agree with all the things he says, but you’ll certainly enjoy how well-reasoned they are and how much thought clearly went into them.

The Big Picture is likely to lead to a lot of interesting, tangential conversations with the folks around you. It certainly had that effect for me. Its density of ideas, however, means it's not a quick read. Even as someone already familiar with many of these concepts, I found myself having to re-read paragraphs or pause to think in order to understand everything.

Carroll asks the reader to juggle a lot of concepts at once, which takes effort but is ultimately rewarding. It feels like a difficult workout at the gym, but for your mind. There are places in the book where you’ll have to put in effort to understand a point, but once you do, you’ll be glad you did.

Listing image by Penguin Random House