In chapter 5, Wilson outlined how science can help us understand the mind. He noted that it is far easier to use a top-down method of exploration than a bottom-up method when trying to understand any complex system, especially the mind. The reason is that when you start at the most complex level and work your way down to the more basic components, it's simple to stay on track. However, when you start with the basic components and try to work your way up, there can be near infinite paths to choose from and it may be impossible to arrive at the correct answer.
Wilson called prediction by the bottom-up method "consilience by synthesis" and he noted that it is extremely difficult to achieve. He noted that one pitfall of this method is that it is conceivable that scientists could construct an algorithm explaining how nature constructed a specific organism and this model might end them up at the correct outcome. However, it is nearly impossible to know if the algorithm is the same one that is found in nature. To explain this point, Wilson described a painting of a flower that is as beautiful and life-like as one found in nature. So life-like in fact that it fools the eye from a distance. However, the algorithm used to create the painting is vastly different from that found in nature. I would say that an even better example would be silk flowers, which are even more near-to-life than paintings.
Next, Wilson explained proximal and ultimate explanations. He described proximal explanations as those that examine how something is produced in nature. Ultimate explanations are those that examine why something evolved in an organism. For instance, Wilson discussed dreams. Scientists now have a fairly good proximal understanding of dreams. We know which chemicals and which parts of the brain are responsible for creating dreams. However, we do not know why humans evolved to have dreams.
Another example Wilson provided was that of biologists and nerve cells. Biologists have a good understanding of how nerve cells work (proximal) but they do not know why these nerve cells work together to create a consciousness in human beings.
Wilson said that biology may be the lynch pin to consilience. Biology as a field is excellent at reductionist science. Biology may also be key in proving Complexity Theory, which Wilson defined loosely as the search for common algorithms across nature. Wilson thinks that biology can provide what is missing in this theory: empirical data.