In Federalist No. 18, Hamilton and Madison team up to address the ongoing issue of the insufficiency of the present confederation to preserve the union.

One of the key takeaways from this essay is summed up in these words a weak government, when not at war, is ever agitated by internal dissentions, so those never fail to bring on fresh calamities from abroad. As proof of the pudding they offer, they recount a history of Greece and how the relatively weak union they formed eventually broke down as rival city states went to war. Had Greece … been united by a stricter confederation, and perservered in her union, she would have never have worn the chains of Macedon, and might have proved a barrier to the vast projects of Rome.

The majority of the essay is spent recounting the histories of the Grecian republics, and the battle between Athens and Sparta and the Achaean league in particular, because it teaches more than one lesson. It emphatically illustrates the tendency of federal bodies rather to anarchy among the members, than to tyranny in the head. As a result, there should be little concern about the Union trying to abuse the power it is given. The essay is a good read, and a great refresher on some of the finer points of historical inquiry, but if you’re in a hurry you can skip the history lesson and get right to the takeaway – a strong Union is always better than a weak confederacy.

In Federalist No. 17, Hamilton again continues his discussion of the insufficiency of the present confederation to preserve the union.

In this essay, he moves on from the discussion of the ability of a loose confederacy to both claim and protect the territories, posts, and natural resources that it should be entitled to and away from the discussion of the increased risk of Civil War presented by a loose confederacy to address the objection that the government of the Union [may be] too powerful and enable it to absorb those residuary authorities, which it might be judged proper to leave with the States for local purposes.

To this end, Hamilton admits that he is at a loss to discover what temptation the persons entrusted with the administration of the general government could ever feel to divest the States of the authorities of that description. He notes that commerce, finance, negotiation, and war seem to comprehend all the objects which have charms for minds governed by that passion; and all the powers necessary to those objects ought, in the first instance, to be lodged in the national depository. After all, we must deal with foreign nations as one nation, or we are no better than a collection of loose confederacies, regardless of what title we convey on the union.

Furthermore, the administration of private justice between the citizens of the same State, the supervision of agriculture and of other concerns of a similar nature, all those things, in short, which are proper to be provided for by local legislation, can never be desirable cares of a general jurisdiction. As such, the Union would see no benefit in pursuing them at the federal level, so there should be no cause for concern because it is therefore improbable that there should exist a disposition in the federal councils to usurp the powers with which they are connected; because the attempt to exercise those powers would be as troublesome as it would be nugatory.

But even, for argument’s sake, if we assume that mere wantonness and lust of domination would be sufficient to beget that disposition, it is the case that it will always be far more easy for the State governments to encroach upon the national authorities than for the national government to encroach upon the State authorities.

Furthermore, there is one transcendent advantage belonging to the province of the State governments, which alone suffices to place the
matter in a clear and satisfactory light, — I mean the ordinary administration of criminal and civil justice. This, of all others, is
the most powerful, most universal, and most attractive source of popular obedience and attachment. As a result, this great cement of society, which will diffuse itself almost wholly through the channels of the particular governments, independent of all other causes of influence, would insure them so decided an empire over their respective citizens as to render them at all times a complete counterpoise, and, not unfrequently, dangerous rivals to the power of the Union.