The Science of Can and Can't by Chiara Marletto
Counterfactual explanations are about what physical events could or couldn't be made to happen.
Imagine looking at the world not just for what it is or how it moves, but for what it could do. What if we focused on possibilities what can happen, or what can’t? This is the bold idea at the heart of Chiara Marletto’s book The Science of Can and Can’t.
She introduces counterfactuals as a new way to think about physical systems that could change how we understand information, energy, knowledge and even creativity. Let’s break it down in simple terms and see how this matters to us.
What Are Counterfactuals?
Counterfactuals are about what a physical system can or cannot do, beyond its current state or motion. Think of a light switch: it’s either ON or OFF, but what makes it special is that it can flip between those states, and its state can be copied to another switch. These abilities flipping and copying are counterfactual properties, and they’re what make the switch a “bit” of information.
Chiara argues that science has overlooked these properties for too long. By focusing on them, we can tackle important problems in physics, like how information works, how energy is conserved, or what knowledge really is.
Counterfactuals Are Game-Changer
Counterfactuals let us bring ideas that seem abstract like information or knowledge into the physical world. Here’s how they work:
Information Is Physical: A bit of information, like a switch being ON or OFF, isn’t just an idea, it depends on physical laws. For a system to be a bit, it must be able to flip between two states and copy those states to another system.
Precise Laws for Big Concepts: Things like energy, heat, or work often feel like rough approximations because they deal with the messy, everyday world. Counterfactuals let us write exact laws about them. For example, we can define how a system stores or transfers information in a clear, scientific way.
Connecting the Clue: Counterfactuals use the same logic for different ideas information, energy, knowledge. You identify what a system can do (like flipping or copying), then write laws about those abilities. This ties together concepts that seem unrelated, creating a unified way to think about the universe.
Counterfactuals in Action
Chiara shows how counterfactuals are already central to some of the biggest questions in physics:
Information Interoperability: Systems like bits can work together to store or transfer information, whether they’re made of photons, electrons, or switches. This ability to “play nice” is a counterfactual property.
No-Cloning in Quantum Physics: In quantum systems, some information can’t be copied perfectly. This “no-cloning” rule is a counterfactual property that shapes how quantum computers work.
Energy Conservation: The difference between work (useful energy) and heat (less useful energy) comes down to what transformations are possible, another counterfactual idea.
Knowledge Resilience: Knowledge is information that lasts, like genes that survive generations or ideas that stick in our minds. Its ability to endure is a counterfactual property.
Explaining Physics With New Possibilities
Chiara has a daring idea: what if all physics laws could be written using counterfactuals? Instead of focusing on how things move (like Newton’s laws), we could focus on what’s possible or impossible. This could simplify tricky problems, like combining quantum theory (which describes tiny particles) with gravity (which describes planets and stars). These two theories don’t mix easily today, but counterfactuals might help by focusing on what systems can do, even if we don’t know all the details of their motion.
Can We Test These Theory?
Yes! Counterfactual laws are like “rules about rules.” Take energy conservation: we test it by comparing a model where energy stays constant to one where it doesn’t. Experiments, like watching a pendulum swing, confirm that energy doesn’t just appear or vanish.
Counterfactuals work the same way. For example, the interoperability law says that if two bits can each store information, their combined system should too. If an experiment shows otherwise, the law might be wrong. This testability makes counterfactuals scientific, not just philosophical.
A real example is the discovery of the neutrino. Scientists noticed that a neutron’s decay didn’t conserve momentum unless a third, nearly massless particle the neutrino was involved. Counterfactuals can lead to breakthroughs like this by predicting what’s possible or not.
Beyond Physics
Counterfactuals don’t just help with physics they could transform how we think about knowledge and creativity. Chiara defines knowledge as information that lasts, like genes or ideas that survive over time. This makes knowledge a physical thing, not something mystical or “human-centered.”
This shift opens up big possibilities:
Knowledge as Science: By defining knowledge through counterfactuals, we can study it objectively, free from subjective or spiritual baggage.
Creativity as a Physical Process: Questions like “How do brains create new ideas?” or “Can computers be creative?” become scientific problems. Could we build AI that creates knowledge? Could we preserve knowledge beyond death by copying it?
Building a Lasting Future: Understanding creativity is key to making our civilization’s achievements endure. If we nurture creativity, we can keep building better futures.
Endings That Spark New Beginnings
Chiara ends her book with a beautiful idea: life is like a journey, and endings can be new starting points. She compares two ancient stories:
Alexander the Great: In a poem by Giovanni Pascoli, Alexander conquers the world but feels empty at the end. His journey didn’t create new possibilities, so he’s left with no dreams to chase.
Odysseus’s Journey: In Homer’s Odyssey, Odysseus faces countless challenges but returns home wiser. His journey, called a “nostos” (a return), is richer at the end because he’s gained knowledge that opens new possibilities.
Reading Chiara Marletto’s book is like a nostos. As you turn the last page, you’re not just done you’re an explorer returning home, carrying new ideas that spark curiosity. The book’s end is a new beginning, urging you to ask, “What else is possible?”
Conclusion
Counterfactuals give us a new lens to see the universe. They make abstract ideas like information and knowledge part of physics, offer new ways to solve tough problems, and inspire us to think about creativity and human progress. Your mind, capable of creating knowledge, is a powerful physical system. Nurture it.
As you close the book, you’re like Odysseus docking at the harbor, ready to set sail again. The world is full of possibilities waiting for you to explore. So, dare to ask: What can I create next?
May these ideas light your path forward.
I hope this book will transform your world view as it done of mine.
Happy Reading !