Since the term irrationalism is often used as a derogatory accusation to criticize other positions as unreasonable, unscientific and thus wrong, it is controversial as a scientific category, especially in individual cases.
Friedrich Engels polemicized that Schelling's 1854 lecture, known as "Philosophie der Offenbarung", was the "first attempt to smuggle belief in authority, emotional mysticism, and gnostic fantasy into the free science of thought.
György Lukács has argued that the first period of irrationalism arose with Schelling and Kierkegaard, in a fight against the dialectical concept of progress embraced by German idealism.
As alternatives to descriptive and normative explanations of the world, some “higher” cognitive functions such as essential perception, faith, intuition or “direct experience” are suggested.
This position is taken by mystical thinkers (Eckhart, Boehme), the neoplatonists (Plotinus, Paracelsus), the romantic philosophers (Schelling) and spiritualists (Bergson).
In his 1886 book, Beyond Good and Evil, Nietzsche emphasized that humans by nature are irrational and criticized attempts of "rationality" of trying to neglect the fact.
In his 1889 novel, Il piacere, which is determined to be partly autobiographical,[34][35] Gabriele D'Annunzio describes how the aesthete lets himself be guided only by the perennial flow of sensations, without following a logical or moral order.
[36][37] In the artistic-literary field, the theme of irrationalism, as a reaction to the positivist and rationalist tendencies of bourgeois society, is found both in decadentism and especially in its counterpart: futurism.
The use of "free words" testifies, for example, to the will to transgress the logic of syntactic-grammatical constructs, while activism and the intoxication of living are celebrated as key elements of its manifesto.
In his 1953 work, The Destruction of Reason, György Lukács aimed to demonstrate how the widespread irrationalism in the West, from Friedrich Schelling to Nietzsche, was nothing other than an expression of the crisis experienced by the bourgeois class, which attempted to justify its existence by will to power and imperialist politics.
[57] Karl Popper also leveled accusations of irrationalism at the philosophies of Hegel and Marx, for having elevated contradiction to a fundamental characteristic of reality.
[58] Question regarding irrationalism were debated particularly in the twentieth century due to its political connection to the founding ideologies of the main totalitarian states of Europe, that had come into being after the outcome of the First World War, namely the Third Reich (Nazism), the Kingdom of Italy (Fascism)[59] and the Soviet Union (Communism).
[60] Nazism openly referred to the thought of Friedrich Nietzsche, or rather to the version distorted by his sister Elisabeth Förster-Nietzsche,[61] and also to Oswald Spengler's work The Decline of the West.
[62][44] By referring to the irrationalist theories of German vitalism (Lebensphilosophie), these works built a narrative that all civilizations go through a natural cycle of development, flowering and decadence, and that Europe, victim of a narrow materialism and urban chaos, was in the last stage: the winter of a world that had known more fruitful seasons.
Europe, unless it managed to purify itself and restore its spiritual values and its original stock, would fall prey to savage policies and wars of annihilation.
[63] Influenced by Goethe, Wilhelm Dilthey, Nietzsche (in particular by his theory of the Eternal Return) and Greek thought, Spengler understood history as a constant process of decay to which it was necessary to react with the establishment of a strongly authoritarian state, partly close to that predicted by the Nazis.
[64] György Lukács pointed to combined notions of Oswald Spengler, Martin Heidegger (existentialism), Ludwig Klages (interwar Lebensphilosophie) of giving Nazis the means of mythologizing history to their will, by exploiting epistemology for sake of historical relativism.
Lukács stating that; With Spengler, real history was supplanted by the myths; with Heidegger it sank into unauthenticity; with Klages it was presented as a set of parables on the Fall of man resulting from the dominance of reason and the infamous intellect.Italian Fascism saw Georges Sorel's "philosophy of violence" as the basis of its ideology, while Marxism had to deal with the irrationalist theories of anarchist-revolutionary communism as theorized by Mikhail Bakunin.