Ken Schwaber, Jim Highsmith and other experts have explained in their books that a lot of agile concepts have been copied from the study of complex systems. However, agile software development has not covered all there is to learn. I will show why practices must be agile (self-organized) *and* formal (controlled), why any software development method is doomed to fail, why managing scope is a too simplistic interpretation of the principle of “embracing changeâ€, why most process improvement initiatives are linear and wrong, and why some sets of practices will be show chaotic behaviour when combined. I will go a step further than what has already been described in mainstream literature, linking some of complexity theory with down-to-earth experience from the trenches in my role as chief information officer for a software development company.