Can we 'see' photons, black holes, curved spacetime, quantum jumps, the expansion of the universe, or quanta of space? Physics challenges appearances, showing convincingly that our everyday vision of reality is limited, approximate and badly incomplete. Established theories such as quantum theory and general relativity and investigations like loop quantum gravity have a reputation of obscurity. Many suggest that science is forcing us into a counterintuitive and purely mathematical understanding of reality. I disagree. I think that there is a visionary core at the root of the best science. Where 'visionary' truly means formed by visual images. Our mind, even when dealing with abstract and difficult notions, relies on images, metaphors and, ultimately, vision. Contrary to what is sometimes claimed, science is not just about making predictions: it is about understanding, and, for this, developing new eyes to see. I shall illustrate this point with some concrete cases, including the birth of quantum theory in Einstein’s intuition, curved spacetimes and quanta of space.

Sophie Hackford explores the idea that the way that computers see the world is becoming our dominant reality. The idea that a physical object, and its data ‘exhaust’, are in constant dialogue with each other. As machine autonomy creeps into our everyday lives, we are creating a physical internet, where people, objects, vehicles move as seamlessly in the real world as data moves around the internet. Digital bots or ‘agents’ might represent us in interactions with our banks, friends, colleagues. Autonomous companies might soon be big players in the economy. Hackford will explore a world where human and machine ‘vision’ will collaborate, compete and even merge together.

When Turner daubed a red buoy in his seascape Helvoetsluys, what did he mean? In nature, red may repel or attract, signalling toxicity or ripeness, anger, ruddy health or sexual readiness. For Turner, the red created contrast, and in making that mark, he meant to generate salience and arouse interest, to dominate his rivals and draw in his admirers. Colour has long excited emotions and intellectual debate, not only for visual art, but also in philosophy, psychology and physiology. In contemporary vision science studies, colour helps people find objects faster, discern material properties, learn, conceptualise and memorise. Yet colour is made in the mind, not out there in the world. It is a subjective phenomenon, a personal possession, one that varies between individual eyes, and one that people cling to with ardour when challenged: witness the public divide over the 'blue/black', 'white/gold' dress. So the question is not only what does colour mean, in life and in art, but how does it mean anything? How does the human brain create colour, stabilise it, and make its meaning? And why does it evoke emotion and aesthetic appreciation?

Eyes abound in the animal kingdom. Some are large as basketballs and others are just fractions of a millimetre. Eyes also come in many different types, such as the compound eyes of insects, the mirror eyes of scallops or our own camera-like eyes. Common to all animal eyes is that they serve the same fundamental role of collecting external information for guiding the animal’s behaviour. But behaviours vary tremendously across the animal kingdom, and it turns out this is the key to understanding how eyes evolved. In the lecture we will take a tour from the first animals that could only sense the presence of light, to those that saw the first crude image of the world and finally to animals that use acute vision for interacting with other animals. Amazingly, all these stages of eye evolution still exist in animals living today, and this is how we can unravel the evolution of behaviours that has been the driving force behind eye evolution.

The 34th Darwin College Lecture Series, held in 2019, addressed Vision. The aim of these lectures, as with all the Darwin College Lectures, was to provide an interdisciplinary study. The lectures range widely: they survey the mechanisms of visual perception, and the evolution of eyes; they address the mental processes underpinning vision, and the nature and significance of private visions and hallucinations; they explore the vision and imagery of artists and of scientists in their endeavours to elucidate the world. The discussions encompass astronomical observation, which enables us to look back over the evolution of the Universe to the earliest epochs, and they extend to foresight, with a vision of a digital future. We conclude this volume with a review of the current developments of computer vision, which increasingly underpin our day-to-day experience of surveillance and of automation.

The brain strives to become a model of the world in which it must survive. It is often more important for it to be functional and efficient than it is to be factually correct. Indeed, there are numerous instances in which it seems to favour usefulness over accuracy, expectation over actuality. This has led many to conclude that even normal perception has a constructive or hallucinatory quality. In extremis, under the influence of fatigue, fear, illness or drugs, an entire reality may be created, one that seems to conflict with the reality accepted by those around us. This condition, known as psychosis, offers us important glimpses into the mechanisms of the mind and the many ways in which they may be altered.