Among his other duties and endeavors, a thus muzzled Kant turned his attentions to formulating what was necessary to achieve perpetual peace in a world full of nation-states. The document can be viewed as a whole here: Perpetual Peace: A Philosophical Sketch (1795). It struggled with basic questions like how one translates a set of ideas in the heads of certain people into lived reality for everyone. The document concluded:
If it is a duty to make real (even if only through approximation in endless progress) the state of public law, and if there is well-grounded hope that this can actually be done, then perpetual peace, as the condition that will follow what has erroneously been called "treaties of peace" (but which in reality are only armistices), is not an empty idea. As the times required for equal steps of progress become, we hope, shorter and shorter, perpetual peace is a problem which, gradually working out its own solution, steadily approaches its goal. (Emphasis mine.)Though Kant was explicitly instructed not to theorize about the nature of true religion, he was able to theorize about a quintessentially religious topic: the nature of a state of existence devoid of violence, characterized by perpetual peace, which had been called the Kingdom of God by former thinkers like St. Augustine, and would be called as much by later thinkers like G.W.F. Hegel. The irony was that the authorities do not seem to have objected, which was probably because they did not know enough to draw the connection themselves. Not free to question the peculiar dogmas of the Christian faith, like the deity of Christ, the character of worship, and the nature of morality, Kant was nonetheless free to theorize about a state of peace in which the self is one with the world and the world with the self.
The Kantian coup d'etat was accomplished through sheer force of intellectual modesty. Kant claimed not to be talking about ultimate bliss, harmony, or peace; he claimed to be merely sketching out how the same might be achieved in this world. This sort of argument only flies, however, if your audience already agrees with the basic premise that religion has nothing to do with what might be achieved in this world. The following passage illuminates the nature of Kant's this-worldliness:
The state of peace among men living side by side is not the natural state (status naturalis); the natural state is one of war. This does not always mean open hostilities, but at least an unceasing threat of war. A state of peace, therefore, must be established, for in order to be secured against hostility it is not sufficient that hostilities simply be not committed; and, unless this security is pledged to each by his neighbor (a thing that can occur only in a civil state), each may treat his neighbor, from whom he demands this security, as an enemy.Here we find Kant thinking about an original state in the larger context of argument that thinks forwards towards a desired end state. The above passage contains reference to old ideas about 'the state of nature', which thinkers like Thomas Hobbes and John Locke once debated with serious intent. 'States of nature' were secularized version of the biblical narratives of the goodness of the creation and the human fallenness. Sometimes emphasis was placed on original goodness, in which case the state of nature was also a state of innocence. Other times emphasis was placed on original fallenness, in which case the state of nature was also a state of war.
Kant's attempts to describe how perpetual peace might be achieved was an inspiration for the failed League of Nations and the moderately successful United Nations in the 20th century. Tellingly, however, 'state of nature' is today nothing more than antiquary curiosity.
As I argued elsewhere, we think as if we are ahead of ourselves. We are either thinking ahead to better days or despairing of the possibility that things might get better; we rarely think backwards with anything more than antiquary curiosity about the bits and pieces our predecessors have left behind.
Kant's coup d'etat contributes to the modern reorientation of our mental landscape. His intellectual modesty has meant we no longer know how the past, present, and future hang together. Though he uses the language of the 'state of nature', Kant no longer means the ways things were in a hypothetical or mythical past. He means the way things are right now, if a universal civil authority over all the world's nation-states was absent. Hobbes and Locke, arguably, meant the something similar; but in deference to their religious heritage, they hypothesized as if the state of nature were found in the distant past.
The ability to think backwards and forwards from the present situation, comparing and contrasting the way things are with the way they might be, and even the way they ought to be, is at the heart of religious belief. That is why Kant's proposal for perpetual peace, though it should strike us as fundamentally religious, comes across, in fact, as a modest secular proposal.
Nothing audacious, nothing untowards. Just a slow ascent into a state of purely civil interactions between persons, each acting with restraint towards others, as if everyone else were autonomous, self-determining agents, and not means to some other self-aggrandizing end--be that fame, fortune, pain, pleasure, power, etc.--which, when you think about it really hard, does sound a lot like religious promises about a world better than the present one.