However whilst the example of subjective secrecy that Kant initially gives concerns authors the discussion that he next opens does not concern them but rather focuses on readers. What he declares to be the "sole article" of this kind that concerns perpetual peace is that the maxims of philosophers concerning the conditions under which public peace is possible should be consulted by states that are arming for war. This "sole article" is understood to involve secrecy in the sense that rulers of states will not wish to make evident the reference to advice that emerges from their subjects. So, rather than openly acknowledging the use of such statements from philosophers it will rather be the practice of states to only tacitly allow the debates of philosophers to take place without indicating that they are in sense being guided by such.
The point about this so-called "secret article" is that it is aimed at making manifest the need for publicity concerning the philosophical debate over the nature of public peace! This "secret article" is also indicated to be based on "universal (morally legislative) human reason" (Ak. 8: 369). So not only is the content of the article officially public it is something indicated to be based effectively on the moral common sense of humanity.
After inserting a discussion of the way in which philosophy is subordinate in practice to other powers in the state Kant returns to the point that rulers should enable the class of philosophers to both exist and debate, not least because philosophers are, he states, incapable of forming seditious factions or clubs. Hence philosophers are not agents of propaganda.
This "secret article" can hardly be understood other than as a reversion to the statement of the first paragraph of Perpetual Peace where Kant argued that since the worldly-wise statesman looks down on the philosopher due to the latter's ineffectual ideas that they cannot consistently state that they face danger from such ideas! In articulating the need for such publicity for philosophy Kant doubtless had in mind the suppression many thinkers faced across Europe in the wake of the French Revolution. There is also ancient precedent as the Roman emperor Domitian exiled philosophers from his polity on the grounds that they were in fact agents of sedition.
The general importance of this "secret article" is the way it introduces the topic of publicity into the discussion of perpetual peace, hence paving the way for the turn, in the appendix, to the formulas of publicity that were discussed in previous postings.