I can’t think of a topic more daunting than one that combines cosmology and philosophy. The former has as its object of study ‘the Universe’, something that is defined as all that exists or, better said, everything that exists in a physical sense—a terrible lot to analyze! The latter is no less boggling. It deals with questions relating to existence, knowledge and ethics—oh, vast notions! Philosophy of Cosmology goes beyond focusing on all things that exist in the physical sense; it encompasses the ‘metaphysical sense’ too.
Though intimidated by the topic, a recent book review in The Economist reminded me I had, for some now obscure reason, been interested in Philosophy of Cosmology a while back. Or, at least, I was then curious enough to print a 50-page manuscript on ‘Issues in the Philosophy of Cosmology’ written in 2006 by the brilliant cosmologist George Ellis. It was not until yesterday that I properly read the text. And it was not until today that I felt brave enough to write a post about the relation between cosmology and philosophy.
The Economist review, labelled under ‘Physics and Philosophy’, introduces a book by David Deutsch entitled ‘The Beginning of Infinity: Explanations That Transform the World’. In doing so, it briefly discusses whether or not science is limited. They write: “recent arguments have examined not only whether the discipline itself is limited—or, indeed, whether the explanation of everything so lusted after by scientists actually exists—but also whether the human mind is equipped to understand everything.” (Deutsch himself is of the opinion that science is infinite. I suppose I have to read his book to understand what that means.)
Cosmology fits nicely into all of this. Once seen as a “speculative enterprise”—indeed, it is still studied in the realm of philosophy and metaphysics—it changed “into a data-driven science that is part of standard physical theory,” to quote from Ellis’ article. But cosmology cannot be seen only as a scientific subject because cosmology as a science is limited.
Classifying the discipline as a science is iffy in itself. Its object of study is unique (there is only one Universe that we can observe) and it can’t be subject to scientific experimentation (we can’t re-run the Universe). Still, as Ellis mentions, modern cosmology is data-driven, which does give it scientific credibility. For example, the standard cosmological theory for the beginning of the Universe, the Big Bang model, was preferred to the alternative, the Steady State model, because of observational tests. The latter states the Universe has no beginning and no end, it is unchangeable. The Big Bang theory, on the other hand, claims the Universe originated in a hot and dense state, very different from what we see today. The discovery of the cosmic microwave background radiation (CMB), a remnant from a period in the history of the Universe when its temperature was higher than at present, killed the Steady State theory.
The modern view may be that cosmology is a science, but it is also that it is not only a science. As cosmologist Sean Carroll writes in his blog, “[cosmology] has extended beyond the observable part of the universe.” There are questions being asked and theories being proposed about stages in the history of the Universe that we cannot reach and places that we cannot observe. So we make philosophical assumptions about it.
One of these assumptions is the cosmological principle, a premise rooted in all cosmological models. Typically, it is stated as “Viewed on a sufficiently large scale, the properties of the Universe are the same for all observers.” As far as we can see, this is a plausible assumption: for example, the large-scale distribution of galaxies looks the same whether we point a telescope to our right or to our left. But it is still just that, an assumption. We cannot possibly confirm that it is true because we can only see small parts of the whole that is the Universe. Wikipedia quotes astronomer William Keel explaining that the cosmological principle “amounts to the strongly philosophical statement that the part of the Universe which we can see is a fair sample, and that the same physical laws apply throughout.” He adds: “In essence, this in a sense says that the Universe is knowable and is playing fair with scientists.” If it weren’t for philosophical choices, cosmology—the science—could not progress.
By bringing philosophy to the table, we give a wider scope to cosmology because philosophy carries questions that cannot be treated scientifically. Why do physical laws exist? What was there before the Big Bang? Why does the Universe allow the existence of intelligent life? Why does anything exist? Tackling these queries results in philosophical assumptions becoming dominant in cosmology “precisely because the experimental and observational limits on the theory are weak,” as Ellis explains in his essay. The more we aim to understand the Universe, the more we have to move from the terrain of physical science to the realm of metaphysics.
If science is limited in that it doesn’t consider metaphysical questions, metaphysics is limited in that it cannot provide definite answers to its questions. And if there is no certainty in metaphysics, there can be no certainty in the cosmological issues it brings about. Ellis concludes: “Ultimate uncertainty is a key aspect of cosmology.” We should learn to love uncertainty (or so say the “leading thinkers”) in order not to feel fear or disappointment when trying to understand the Universe.
Whether the human mind will ever be able to hold the key to absolute understanding is a whole different matter. Writing about a talk given by astronomer Sir Martin Rees, Sean Carroll notes “even if there is an ultimate explanation in the theory-of-everything sense, it may simply be too difficult for our limited human minds to understand.”
As someone who felt overwhelmed simply from writing about the basics of Philosophy of Cosmology, I can say, with all certainty and no fear, that my mind is too limited to fully grasp the physical or metaphysical Universe.