Uncertainties of this chapter

In earlier chapters of this book what I have said can mostly be said with absolute certainty, since it is based on observations about the behavior of purely abstract systems that I have explicitly constructed. But in this chapter, I study actual systems that exist in nature, and as a result, most of what I say cannot be said with any absolute certainty, but instead must involve a significant component of hypothesis. For I no longer control the basic rules of the systems I am studying, and instead I must just try to deduce these rules from observation—with the potential that despite my best efforts my deductions could simply be incorrect.