Fiat iustitia, et pereat mundus. It means just what it says. Ferdinand I was a Catholic absolutist.
Justice is for and of god. Kant's twist is silly, Arendt's obliviousness to history is just odd. Spinoza was writing after Westphalia.

Arendt, Truth and Politics

The subject of these reflections is a commonplace. No one has ever doubted that truth and politics are on rather bad terms with each other, and no one, as far as I know, has ever counted truthfulness among the political virtues. Lies have always been regarded as necessary and justifiable tools not only of the politician's or the demagogue's but also of the statesman's trade. Why is that so? And what does it mean for the nature and the dignity of the political realm, on one side, and for the nature and the dignity of truth and truthfulness, on the other? Is it of the very essence of truth to be impotent and of the very essence of power to be deceitful? And what kind of reality does truth possess if it is powerless in the public realm, which more than any other sphere of human life guarantees reality of existence to natal and mortal men–that is, to beings who know they have appeared out of non-being and will, after a short while, again disappear into it? Finally, is not impotent truth just as despicable as power that gives no heed to truth? These are uncomfortable questions, but they arise necessarily out of our current convictions in this matter.

What lends this commonplace its high plausibility can still be summed up in the old Latin adage "Fiat iustitia, et pereat mundus" ("Let justice be done though the world may perish"). Apart from its probable author in the sixteenth century (Ferdinand I, successor to Charles V), no one has used it except as a rhetorical question: Should justice be done if the world's survival is at stake? And the only great thinker who dared to go against the grain of the question was Immanuel Kant, who boldly explained that the "proverbial saying ... means in simple language: 'Justice shall prevail, even though all the rascals in the world should perish as a result.' " Since men would not find it worth while to live in a world utterly deprived of justice, this "human right must be held sacred, regardless of how much sacrifice is required of the powers that be . . . regardless of what might be the physical consequences thereof."[1] But isn't this answer absurd? Doesn't the care for existence clearly precede everything else–every virtue and every principle? Is it not obvious that they become mere chimeras if the world, where alone they can be manifested, is in jeopardy? Wasn't the seventeenth century right when it almost unanimously declared that every commonwealth was duty bound to recognize, in Spinoza's words, "no higher law than the safety of [its] own realm"? [2] For surely every principle that transcends sheer existence can be put in the place of justice, anq if we put truth in its place–"Fiat veritas, et pereat mundus"–the old saying sounds even more plausible. If we understand political action in terms of the means-end category, we may even come to the only seemingly paradoxical conclusion that lying can very well serve to establish or safeguard the conditions for the search after truth–as Hobbes, whose relentless logic never fails to carry arguments to those extremes where their absurdity becomes obvious, pointed out long ago.[3] And lies, since they are often used as substitutes for more violent means, are apt to be considered relatively harmless tools in the arsenal of political action.

Reconsidering the old Latin saying, it will therefore come as something of a surprise that the sacrifice of truth for the survival of the world would be more futile than the sacrifice of any other principle or virtue. For while we may refuse even to ask ourselves whether life would still be worth living in a world deprived of such notions as justice and freedom, the same, curiously, is not possible with respect to the seemingly so much less political idea of truth. What is at stake is survival, the perseverance in existence (in suo esse perseverare), and no human world destined to outlast the short life span of mortals within it will ever be able to survive without men willing to do what Herodotus was the first to undertake consciously–namely λἐγειν τα ἐὀντα,  to say what is. No permanence, no perseverance in existence, can even be conceived of without men willing to testify to what is and appears to them because it is.
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1. Eternal Peace, Appendix I 

2. I quote from Spinoza's Political Treatise because it is noteworthy that even
Spinoza, for whom the libertas philosophandi was the true end of government,
should have taken so radical a position. 

3. In the Leviathan (ch. 46) Hobbes explains that "disobedience may lawfully be
punished in them, that against the laws teach even true philosophy." For is not "leisure the mother of philosophy; and Commonwealth the mother of peace and leisure"? And does it not follow that the Commonwealth will act in the interest ofphilosophy when it suppresses a truth which undermines peace? Hence the truthteller, in order to cooperate in an enterprise which is so necessary for his own peace of body and decides to write what he knows "to be false philosophy." Of this Hobbes suspected Aristotle of all people, who according to him "writ it as a thing consonant to, and corroborative of [the Greeks'] religion; fearing the fate of Socrates." It never occurred to Hobbes that all search for truth would be self-defeating if its conditions could be guaranteed only by deliberate falsehoods. Then, indeed, everybody may turn out to be a liar like Hobbes' Aristode. Unlike this figment of Hobbes' logical fantasy, the real Aristotle was of course sensible enough to leave Athens when he came to fear the fate of Socrates; he was not wicked enough to write what he knew to be false, nor was he stupid enough to solve his problem of survival by destroying everything he stood for.

On Charles V

When he renounced his crown in 1555, retiring to a monastery he took nine of Titian’s paintings with him, including the monumental ‘Triumph of Faith”, La Gloria”, “and he is said to have looked at it in his dying days with such persistence and intensity of feeling that his doctors took fright.”