It is evident that the notion of a certain ignorance, of a «not knowing» of the thinking subject, has been recognized since Antiquity, and that the germ of the Freudian unconscious is in what precedes it, however, it is rather a question of the non-conscious. Brès (2006: 12-30) and Lacan (1993: 55) have pointed out that there was only a need to create a notion of the unconscious after Descartes, fundamentally at the moment when the identification of psychism and consciousness is made. In other words, before Descartes and Locke, non-consciousness did not require the creation of a notion of the unconscious, so the conditions of possibility of psychoanalysis arise with modern science, which in turn begins after Descartes (Lacan, 1993).
It was coined before Kant, however, Th. Adorno (2010: 89) states that the main reason that led to the formation of the «philosophies of the unconscious» is «the opposition to the first philosophy of consciousness that was consistent: Kant’s doctrine». According to his approach, the philosophical contents criticized by Kant (who never included the notion of the unconscious) and which «did not allow themselves to be incorporated» in a philosophy of consciousness, converged in the formation of the philosophies of the unconscious.
The Freudian unconscious is debated between: (a) An absolute unknowable, the primordial repressed: non-phenomenal and that would seem to resemble the Kantian «thing-in-itself» (Brès, 2006; Adorno, 2010; Le Gaufey, 2008b); a limit concept to which Freud himself seemed to adhere: «The unconscious is the truly real psychic, it is as unknown to us in its inner nature as the real of the external world, and is given to us by the data of consciousness as incompletely as is the external world by the indications of our sense organs» (Freud,  1976: 600), and (b) What is possible to be known: «the inner object is less unknowable than the external world» (Freud, [1915b] 1976: 167). Knowledge that is possible through its connection with words (unlike Kant), the only access to consciousness, and even more, constituted from the relationship with language. But also, the multiple ways to refer to the unconscious: efficacy, deduction, processes, psychic place, facts, motions, acts; as a «wanting» and «thinking», a «knowing» that above all refers to its constitutive laws.
I invite everyone to read Matias’ post with the topic of the day.
Finally, I encourage everyone to reflect on the concept of the day. No one else but us can re-signify our own being