The term is first used by Fichte and has a variety of meanings. It can refer to facts and factuality, as in nineteenth-century positivism, but comes to mean that which resists explanation and interpretation in Dilthey and Neo-Kantianism. The Neo-Kantians contrasted facticity with ideality, as does Jürgen Habermas in Between Facts and Norms (Faktizität und Geltung). It is a term that takes on a more specialized meaning in 20th century continental philosophy, especially in phenomenology and existentialism, including Edmund Husserl, Martin Heidegger, Jean-Paul Sartre, and Maurice Merleau-Ponty. Recent philosophers such as Giorgio Agamben, Jean-Luc Nancy, and François Raffoul have taken up the notion of facticity in new and interesting ways.
Heidegger discusses facticity as the thrownness (Geworfenheit) of individual existence. By this, he is not only referring to a brute fact, or the factuality of a concrete historical situation, e.g., "born in the 50's." Facticity is something that already informs and has been taken up in existence, even if it is unnoticed or left unattended. As such, facticity is not something we come across and directly behold. In moods, for example, facticity has an enigmatic appearance, which involves both turning toward and away from it. For Heidegger, moods are conditions of thinking and willing to which they must in some way respond. The thrownness of human existence (or Dasein) is accordingly disclosed through moods.