The world is confusing and people everywhere seek to understand it, as well as humans' place in it all. To do so, we create a world picture, whether it is an infinite tower of tortoises with the flat earth on their back, or string theory. Although the latter is more precise mathematically, it lacks observational evidence just as much as the former. Yet, the tortoise theory predicts people could fall off the edge of the world, and we know they don't.
Hawking argues that everyone has a theory of the universe, their own worldview, that has inherent predictions about the world and its constituent parts. Scientists’ role is to observe the universe and its phenomena in order to provide accurate and logical world views that offer useful predictions.
The first attempts to explain the world involved unpredictable, humanlike spirits. But later, regularities were noticed, like the sun always rising in the east. Thus it was thought, there might still be gods, but they obeyed strict laws. Over the last 300 years in particular, these laws have been ever more minutely explored.
Since the dawn of the earliest human civilizations, people have created theories of the forces that govern the world’s laws. Over time, these became more rational and scientific, based on direct observation of the universe’s regular cause and effect. The pace of this progress has been exponential.
The successes in that period led some, like Laplace, to think scientists could predict everything, even human behavior, if only they knew the complete make up of the universe at one given point. But his idea did not say how the laws that govern such activity were set, or how the universe looked at the beginning. These aspects were in God's hands, who was largely left to the areas that were not yet understood.
While science gained increasing popularity as an approach to understanding the world, those areas that remained unknown and unknowable (at the time at least) remained within the realm of religious thought. God was useful, like the anthropic principle, for answering certain tricky questions.
Today, Laplace’s approach is defunct because of the uncertainty principle of quantum mechanics, which introduces a minimum level of randomness. Quantum theory gives particles less well-defined positions and velocities to deal with this inherent inability to accurately measure them. But the calculations are more accurate when considering the particles as waves. Perhaps there are no positions and velocities, and there are only waves. The unpredictability comes from a mismatch of preconceived ideas and actual reality.
Over time, science came to incorporate more complex theories, such as the innate randomness in all of the universe’s activities. This necessitated rethinks of many major phenomena and laws. Hawking suggests that despite the lengths science has come, perhaps scientists are still too hesitant to let go of the more entrenched ideas, such as particles. The key to progress is objectivity.
The purpose of science is now to identify the laws that allow us to predict events. But, the question comes back round to how these laws were chosen. Gravity has taken prominence in this book because it forms the large-scale structure of the universe, despite being the weakest of the four main forces. Gravity was incompatible with the previous misconceptions the universe was unchanging.
Modern science is now focused on predicting the universe, within the limits of its randomness. To do so, scientists must look back, to understand how the universe came to be in its current state. Unraveling the mysteries of the early universe could provide crucial clues.
General relativity states there must have been a point of infinite density at the beginning, the big bang. The universe would return to such a point in a big crunch. The theory also predicts other, localized singularities in black holes. The laws of science break down at these singularities, allowing room for God to work.
General relativity is an incomplete theory because it predicts its own breakdown at key moment in the lifecycle of the universe, as described by its own laws. As such, there is plenty of room left for God, as Hawking as shown throughout; religion seems to survive best in the areas remaining unknown.
Introducing quantum mechanics, however, leads to ideas of a finite, four-dimensional space with no boundaries. This could explain much of what we observe, including the wider uniformity of the universe and its irregularities, like stars or people. But if there are no boundaries, there is little room for God. Einstein asked what choice God had when making the universe. If the no boundary model is accurate, the answer is he had no freedom at all over initial conditions, although he could have still created the laws of science.
Hawking quotes Einstein’s question to demonstrate how God has remained within the scientific debate even as his role has diminished. While the big bang fits well with religious teachings, the no boundary concept pushes God even further out of the model. Yet Hawking notes there could still be a creator that determined the rules that govern that universe.
Even if scientists find the unifying theory of physics, it is still just a set of laws. What is it that breathes life into the universe? Would such a theory require a creator? Many scientists are too preoccupied with questions of what, rather than why. Philosophers tend to ask these questions, but struggle to keep up with the fast pace and technical nature of modern scientific discovery.
Even with a unifying theory, questions would remain, such as where that theory itself came from, and why it has the power it does. These are questions philosophers, and by extension religious teachers, consider. By noting this, Hawking argues for a broader discussion on scientific topics, which requires better dissemination of scientific principles and understanding among a wider range of thinkers.
If a complete theory is found, over time it is likely to be distilled in a way that everyone can understand and engage with. Then everyone can discuss the big questions of why we and the universe exist. If humans can find the answer to that, it would be the same as knowing the mind of God.