At first glance, the notion of a physicist wrestling with the properties of light may seem to be as distant from the world of philosophy and art than ever could be.
Niels Bohr, however, stood apart. In the early part of the 20th century, Bohr was developing his theory of complementarity while grappling with the unpredictable nature of light and quantum mechanics, and he turned to the humanities to help. His discoveries and thoughts would transcend beyond just physics into the world of philosophical and artistic thinking. His theory about it would state that two concepts, both seemingly different, could also be mutually complementary. What it means is that an experiment which clearly illustrates one part of nature would simultaneously obscure another complementing view. An example of this is demonstrated through the properties of light. The theory held that light could be both a wave and a particle, but our measurements of it could only reveal one, a wave, for example, while obscuring the other, a particle. His principle implies that while gaining certain information in a particular observation, some other, equally relevant information is simultaneously lost. Light is comprised of both elements, yet we could only measure and witness one at a time. For Bohrs, this principle was also profoundly philosophical, highlighting how many of our perceptions of the world remain unseen and are often only measured by what we immediately wish to see of them. His beliefs and approaches were so deeply felt that when he was bestowed the Danish Order of the Elephant, he chose as his coat of arms the symbol of yin-yang. Inscribed on the crest is the motto Contraria Sunt Complementa which means "opposites are complementary". This approach is something that made Bohr such a visionary, and beloved physicist. It was his willingness to see a dual nature not as a contradiction, but as two sides of the same coin, with only one being visible at a time.
What made him endearing here was his insistence that the language with which we describe things is as important as the physical properties we perceive of them. Many physicists of the early 20th century were grappling with notions of relativity as it applies to observations, and Bohr felt no exception to this. He realized that what we choose to see is always relative to both us as viewers and the subjects we perceive — not merely one or the other — and language was an inherent part of understanding what we see. (This is also a philosophy that runs through the entirety of the two volumes here). Bohr’s perspective endeared to many of his students and colleagues as well, maintaining collaborative and mentoring relationships with them — many of which became great physicists and thinkers themselves. This playful, curious approach was collegial and often interdisciplinary applying not just to physics, but to writing, philosophy, and the understandings of ourselves. Through the nature of complements, Bohr left us with a kind philosophical approach to science that can also serve as an inspiring model to many of our own, living worldviews. For me, it remains the backbone to the works presented here as other models of thought. — michael graf