Ryan Boissonneault's Reviews > Existential Physics: A Scientist's Guide to Life's Biggest Questions

It’s a telling fact that centuries of progress in modern science has left the big questions of metaphysics ultimately unresolved. Questions like: How did the universe begin, and how will it end? Does God exist? Do we have free will? What is consciousness? How do mind and matter interact?

Existential Physics by physicist Sabine Hossenfelder goes a long way in explaining why this is the case. The short answer is that, as physical phenomena become increasingly smaller and more remote—and therefore outside the reach of observation and measurement—we must increasingly look to mathematics for answers. But, as Hossenfelder notes, oftentimes more than one mathematical model can fit the current facts, and, without the assistance of further experiment or observation, there’s no way to verify whether or not the chosen mathematical model is in fact an accurate depiction of reality.

The upshot is, the theory of the multiverse, for example, turns out to be, in a sense, no more scientific than the assertion that God created the universe 6,000 years ago. The multiverse may be more consistent with current science—and is supported by mathematical models—but the point is that, without the possibility of directly observing it, there is simply no way of confirming we have the right mathematical model, or that some other set of equations suggesting some other theory is in fact correct.

Hossenfelder points out that while it may be fun to talk about computer-simulated universes, multiverses, brains-in-vats, and panpsychism, we should remind ourselves that all of these theories reach far beyond what experimental physics can actually confirm. It doesn’t mean that these theories will never be confirmed, but at the moment, they represent pure speculation. And speculation that is mathematically sophisticated is still, in the end, speculation.

Of course, as Immanuel Kant noted, the human mind is burdened by questions that, due to its limitations, it cannot answer, but that due to its nature it also cannot ignore. And so we will likely continue to speculate beyond the facts, often invoking the mysteries of quantum physics as support for a host of quack theories (and ignoring the fact that the behavior of particles doesn’t translate to the behavior of macroscopic objects). But what this book makes clear is that this type of speculation is not limited to the idiocy of common supernatural beliefs, and that even scientists quite frequently cannot resist engaging in wild speculations. It just so happens that they’re better at math than the rest of us, so it’s harder to call them out on it.

But we should also remember that it’s not just our enthrallment with mathematics that’s the problem. There’s also the problem of how subjective experience seems to resist mathematical/mechanical explanations entirely (see the Mary’s room thought experiment). Hossenfelder does a rather poor job of explaining these deeper philosophical issues, but that’s unfortunately what one would come to expect lately from a scientist venturing into the field of philosophy.

There are additional problems. Hossenfelder appears to exempt her own preferred views from the same level of skepticism she applies to the theories of other scientists. For example, she’s uncomfortable with the idea of multiple universes because there’s no experimental data to confirm it. And yet, she’s perfectly ok with the idea that we could replace each one of our neurons with silicon chips and maintain consciousness. If she took her own advice, however, she might realize that the idea of artificially creating consciousness has the same level of empirical support as the multiverse; that is to say, none.

The bottom line: Take the conclusions found in the book for what they’re worth—one scientist’s views on difficult questions that are far from being resolved anytime soon.