The purpose of this chapter is to show that Cornelius Castoriadis offers a particularly innovative response to the question of the socialised individual’s capacity to create newness. I first identify the conceptual apparatus that informs Castoriadis’s thinking, focusing on the notions of the radical imaginary, social imaginary, and radical imagination. I then describe how Castoriadis conceives of the subject in terms of a unified, albeit fluctuating, psychic monad that must be turned into a differentiated individual through a process of socialisation. Rather than annihilate the psychic monad, this process sublimates the psychic monad within the socialised individual, with the consequence that (1) it is necessary to find ways within each social imaginary for the psychic monad to express its radical autonomy, and (2) the individual is always able to “use” its chaotic psychic monadism originally and creatively. It is precisely because the sublimated primal unconscious continues to subtend the socialised psyche that the individual is always able to affect a fundamental rupture from its social imaginary/social unconscious with this rupturing permitting the creation of genuine newness and, indeed, being its condition; that is, it is only because of this rupture that something can be considered to be genuinely creative and new.