All I have been concerned to indicate here is this: in the most spiritual sphere, too, the ascetic ideal has at present only one kind of real enemy capable of harming it: the comedians of this ideal— for they arouse mistrust of it. Everywhere else that the spirit is strong, mighty, and at work without counterfeit today, it does without ideals of any kind—the popular expression for this abstinence is ‘atheism’—except for its will to truth. But this will, this remnant of an ideal, is, if you will believe me, this ideal itself in its strictest, most spiritual formulation, esoteric through and through, with all external additions abolished, and thus not so much its remnant as its kernel. Unconditional honest atheism (and its is the only air we breathe, we more spiritual men of this age!) is therefore not the antithesis of that ideal, as it appears to be; it is rather only one of the latest phases of its evolution, one of its terminal forms and inner consequences—it is the awe-inspiring catastrophe of two thousand years of training in truthfulness that finally forbids itself the lie involved in belief in God…What, in all strictness, has really conquered the Christian God? The answer may be found in my Gay Science (section 357): ‘Christian morality itself, the concept of truthfulness taken more and more strictly, the confessional subtlety of the Christian conscience translated and sublimated in to the scientific conscience, into intellectual cleanliness at any price. To view nature as if it were a proof of the goodness and providence of a God; to interpret history to the glory of a divine reason, as the perpetual witness to a moral world order and moral intentions; to interpret one’s own experiences, as pious men long interpreted them, as if everything were preordained, everything a sign, everything sent for the salvation of the soul—that now belongs to the past, that has the conscience against it, that seems to every more sensitive conscience indecent, dishonest, mendacious, feminism, weakness, cowardice: it is this rigor if anything that makes us good Europeans and the heirs of Europe’s longest and bravest self-overcoming’ All great things bring about their own destruction through an act of self-overcoming: thus the law of life will have it, the law of the necessity of ‘self-overcoming’ in the nature of life—the lawgiver himself eventually receives the call: ‘patere legem, quam ipse tulisti.’ In this way Christianity as a dogma was destroyed by its own morality; in the same way Christianity as morality must now perish, too: we stand on the threshold of this event. After Christian truthfulness has drawn one inference after another, it must end by drawing its most striking inference, its inference against itself; this will happen, however, when it poses the question ‘what is the meaning of all will to truth?’ And here I again touch on my problem, on our problem, my unknown friends (for as yet I know of no friend): what meaning would our whole being possess if it were not this, that in us the will to truth becomes conscious of itself as a problem? As the will to truth thus gains self-consciousness—there can be no doubt of that—morality will gradually perish now; this is the great spectacle in a hundred acts reserved for the next two centuries in Europe—the most terrible, most questionable, and perhaps also the most hopeful of all spectacles.—
Friedrich Nietzsche, On the Genealogy of Morals, pg. 160-161
You heard it here: atheism is the most advanced form of Christianity.