Unexpected events, by standing out against the backdrop of routine and predictable moments, can make us see the originality of every moment, the novelty and unexpectedness of the present in general. Time, says Elizabeth Grosz, is ‘a kind of evanescence that appears only at those moments when our expectations are (positively or negatively) surprised’ (Grosz 2004, 5). This is not, for Grosz, the usual cliché, where a sensation to which we are normally dead comes into being as the defamiliarising effect of the unexpected, or the power of now elevates special people above the mundane. The unexpected, or the ‘untimely’, as she prefers it, is a strand in scientific and philosophical thinking, in Darwin, Nietzsche and Bergson (who she writes about at length), but also in Derrida and Deleuze (who she does not), that seeks to account for change through interruptions in the continuity of time, disruptions of our expectations, or unpredictable emergences in the physical universe. Within this strand of thinking Darwin's account of evolution has a special place, both for its recognition of the accidental, the random and the unexpected in the descent of life and for the introduction of those values into the methodologies of study formerly devoted to the pursuit of stable, predictive laws: