“It seems that only one philosophy can succeed the philosophy of existentialism: nonexistentialism, the philosophy of nonexistent existence.”

Part I : Ambiguity and Freedom
The Ethics of Ambiguity (1947)
Context: From the very beginning, existentialism defined itself as a philosophy of ambiguity. It was by affirming the irreducible character of ambiguity that Kierkegaard opposed himself to Hegel, and it is by ambiguity that, in our own generation, Sartre, in Being and Nothingness, fundamentally defined man, that being whose being is not to be, that subjectivity which realizes itself only as a presence in the world, that engaged freedom, that surging of the for-oneself which is immediately given for others. But it is also claimed that existentialism is a philosophy of the absurd and of despair. It encloses man in a sterile anguish, in an empty subjectivity. It is incapable of furnishing him with any principle for making choices. Let him do as he pleases. In any case, the game is lost. Does not Sartre declare, in effect, that man is a “useless passion,” that he tries in vain to realize the synthesis of the for-oneself and the in-oneself, to make himself God? It is true. But it is also true that the most optimistic ethics have all begun by emphasizing the element of failure involved in the condition of man; without failure, no ethics; for a being who, from the very start, would be an exact co-incidence with himself, in a perfect plenitude, the notion of having-to-be would have no meaning. One does not offer an ethics to a God. It is impossible to propose any to man if one defines him as nature, as something given. The so-called psychological or empirical ethics manage to establish themselves only by introducing surreptitiously some flaw within the manthing which they have first defined.

George Santayana, in his letter to John Boynton Priestley, 15 September 1924
S - Z, George Santayana

Source: Dean of the Plasma Dissidents (1988), p. 192.

Speech in Birmingham (5 March 1925), quoted in On England, and Other Addresses (1926), pp 32-33.
1925
Context: I am whole-heartedly with those men who talk about disarmament on the Continent, peace on the Continent, and the removal of suspicion on the Continent, but far more do I plead for disarmament at home, and for the removal of that suspicion at home that tends to poison the relations of man and man, the removal of which alone can lead us to stability for our struggling industry, and create the confidence in which our people may be able to move forward to better things... It is one of the paradoxes of public life that from the very lips which preach pacifism abroad we hear the cries for war at home. Who was it said of Rousseau that he was a lover of his kind, but a hater of his kin? The children of such a philosophy can only bring damnation to this country.

Ueberhaupt aber bin ich allmälig der Meinung geworden, daß der erwähnte Nutzen der Kathederphilosophie von dem Nachtheil überwogen werde, den die Philosophie als Profession der Philosophie als freier Wahrheitsforschung, oder die Philosophie im Auftrage der Regierung der Philosophie im Auftrage der Natur und der Menschheit bringt.
Sämtliche Werke, Bd. 5, p. 151, E. Payne, trans. (1974) Vol. 1, p. 139
Parerga and Paralipomena (1851), On Philosophy in the Universities

Preface
Democracy's Discontent, 1998

Man hat nur so viel Moral, als man Philosophie und Poesie hat.
“Selected Ideas (1799-1800)”, Dialogue on Poetry and Literary Aphorisms, Ernst Behler and Roman Struc, trans. (Pennsylvania University Press:1968) #62

"Pessimism and Tyranny"
Resistance, Rebellion, and Death (1960)