Jacques Lacan, The Four Fundamental Concepts of Psychoanalysis, trans. Alan Sheridan, ed. Jacques-Alan Miller (Harmondsworth: Penguin Books Ltd., 1987 (1979)), 151.
To name a few of the most prominent thinkers in this field: Gilles Deleuze, for his ontology of the virtual; Alain Badiou, for his mathematical ontology; Giorgio Agamben, for his ontology of potentiality.
Lacan and Freud being, in my opinion, synonymous with "psychoanalysis."
(Psychoanalysis) proceeds from the same status as Science itself. It is engaged in the central lack in which the subject experiences itself as desire... It has nothing to forget (a reference, no doubt, to the Heideggerian "forgetting of Being"), for it implies no recognition of any substance on which it claims to operate, even that of sexuality." Lacan, The Four Fundamental Concepts of Psychoanalysis, 266.
Slavoj Žižek is very right in replacing the term "vital" with the term "undead": What is at stake here is not any kind of simple opposition between life and death, or vital forces and the "dead" automatism of the symbolic, but is instead a paradoxical entity traversal to this divide.
Sigmund Freud, "Three Essays on the Theory of Sexuality," in On Sexuality, Vol. 7, The Pelican Freud Library (Harmondsworth: Penguin Books, 1977), 141.
"It is essential to understand clearly that the concepts 'masculine' and 'feminine,' whose meaning seems so unambiguous to ordinary people, are among the most confused that occur in science."
Ibid, 83. Which is why, "from the point of view of psychoanalysis, the exclusive sexual interest felt by men for women is also a problem that needs elucidating and is not a self-evident fact based upon an attraction that is ultimately of a chemical nature." Ibid., 57.
Lacan, The Four Fundamental Concepts of Psychoanalysis, 204.
Mladen Dolar, "One Splits into Two," in Die Figur der Zwei/The Figure of Two, Das Magazin des Instituts für Theorie, No. 14/15 (December 2010) 88.
The lecture, called "The Sexual Compact," has only been published in Spanish so far, in a collection of Joan Copect's essays titled El Compacto Sexual (Paradiso editores and 17, Instituto de Estudios Criticos, 2011). The English version will appear this spring in a special issue of Angelaki on vitalism and sexual difference.
And, to be said in passing, something very similar happened in the conceptual space of leftist political theory when it abandoned all reference to the political economy and focused entirely on the "cultural" (i.e. identity politics), or "evental" (Badiou), dimension of emancipation. Žižek developed this argument very convincingly in chapter 3 of Living in the End Times (London and New York: Verso, 2010.
This paper was originally presented at the conference "One Divides Into Two: Negativity, Dialectics, and Clinamen," held at the Institute for Cultural Inquiry Berlin in March 2011.