Stuart Firestein Science is a fundamentally optimistic enterprise. More than a cheery disposition, it is the source of a philosophical outlook that we might call ‘optimistical’. It reliably produces fundamental and actionable knowledge about the world. We are able to take for granted, in a way even our recent ancestors never imagined, the idea of progress. The engines behind science, surprisingly, are ignorance, the unknown, failure, and, perhaps most vexingly, uncertainty. In recent decades, science has undergone a change in perspective and practice — from viewing the universe like a clockwork regimented by laws and formulas to recognizing it as irreducibly complex and uncertain. Perhaps counter intuitively this has freed science to exploit previously unimaginable possibilities and opportunities. It has led to a deeper understanding of the nature of things and to the production of technologies such as lasers, microchips, the internet, genetics, and many more. And yet socially and societally we remain mired in a 19th century view of deterministic science. We might instead learn to revel in the adventure of navigable uncertainty and take advantage of the creative opportunities of a world where we can confidently say ‘it could be otherwise’. Possibility of this sort is the rarest and purest form of optimism. Stuart Firestein is a neuroscientist and the former Chair of Columbia University’s Department of Biological Sciences, where he researches the vertebrate olfactory system. He is also a member of SFI’s Fractal Faculty.