Large systems evolve from successful, smaller one, an observation predicted by the branch of study known as systems theory. Systems theory also predicts that our systems will inevitably behave, and fail, in unforeseen ways. This talk will draw from the ideas of two very different systems theorists to demonstrate that neither quality architecture nor thorough testing can prevent our software from eventually exhibiting pathological behavior. The first is the safety researcher Sidney Dekker, who proposed a theory of "drift into failure" that describes how seemingly reliable safety-critical systems can still lead to accidents. The second is the late pediatrician John Gall, who coined the "Generalized Uncertainty Principle" about how all types of complex systems behave unexpectedly.Even though failure is inevitable, there is still hope. Chaos Engineering is an approach that can be used to identify system vulnerabilities before they lead to outages. This talk will cover how to design and run Chaos Engineering experiments, drawing examples from our experiences at Netflix.