Sean B. Carroll

We should always admit that we don’t know everything but not be so cautious that we don’t want to admit when we do know things. We know the particles we are made of, and the forces by which we interact. That’s one of the greatest accomplishments in the history of humankind. We can be a little bit proud.

This choice will come into play when we start talking about quantum fields and virtual particles, whose status also raises tricky philosophical questions. For our purposes, it is the wave function that represents reality, and all of our talk of “particles” and “fields” is a useful language for thinking about that reality in relatively intuitive terms. If your favorite formulation of quantum mechanics prefers different ways of talking, you are welcome to translate into whatever language you are comfortable with.

The broader ontology typically associated with atheism is naturalism—there is only one world, the natural world, exhibiting patterns we call the “laws of nature,” and which is discoverable by the methods of science and empirical investigation. There is no separate realm of the supernatural, spiritual, or divine; nor is there any cosmic teleology or transcendent purpose inherent in the nature of the universe or in human life. “Life” and “consciousness” do not denote essences distinct from matter; they are ways of talking about phenomena that emerge from the interplay of extraordinarily complex systems. Purpose and meaning in life arise through fundamentally human acts of creation, rather than being derived from anything outside ourselves. Naturalism is a philosophy of unity and patterns, describing all of reality as a seamless web.

What we can’t do is demand that the universe scratch our explanatory itches. Curiosity is a virtue, and it’s good to look for answers to “Why?” questions whenever we might be able to find them, or when we think that asking such questions might help us to understand things better. But we should be at peace with the possibility that, for some questions, the answer doesn’t go any deeper than “That’s what it is.” We’re not used to that—our intuition assures us that every event can be explained in terms of some reason why. To understand why we have that impression, we need to dig more deeply into how our actual universe has evolved.

The “reasons” and “causes” why things happen, in other words, aren’t fundamental; they are emergent. We need to dig in to the actual history of the universe to see why these concepts have emerged.

Meaning in life can’t be reduced to simplistic mottos. In some number of years I will be dead; some memory of my time here on Earth may linger, but I won’t be around to savor it.

Poetic naturalism is a philosophy of freedom and responsibility. The raw materials of life are given to us by the natural world, and we must work to understand them and accept the consequences. The move from description to prescription, from saying what happens to passing judgment on what should happen, is a creative one, a fundamentally human act. The world is just the world, unfolding according to the patterns of nature, free of any judgmental attributes. The world exists; beauty and goodness are things that we bring to it.

Metaphysical principles are tempting shortcuts but not reliable guides. There are good reasons why things often seem to happen for reasons—and also reasons why that’s not a bedrock principle.

The momentary or Laplacian nature of physical evolution doesn’t have much relevance for the choices we face in our everyday lives. For poetic naturalism, the situation is clear. There is one way of talking about the universe that describes it as elementary particles or quantum states, in which Laplace holds sway and what happens next depends only on the state of the system right now.

What we’re seeing is a manifestation of the layered nature of our descriptions of reality. At the deepest level we currently know about, the basic notions are things like “spacetime,” “quantum fields,” “equations of motion,” and “interactions.” No causes, whether material, formal, efficient, or final. But there are levels on top of that, where the vocabulary changes.