The Constitution of a Perfect Commonwealth is in two parts.
The Preface contains a numerical working through of Spence's plan showing the expected income of different parts of the population at a given level of rent, using input values from a real, though small, village in Leicestershire. The rent levels are assumed to represent real underlying values, though Spence does suggest that the total revenue of the parish might be increased by exploiting commonly owned natural resources such as mines or fisheries. The source of the money needed to pay the rents is never mentioned, and so must be assumed to be the same as before the Plan, whether labouring for wages, manufacturing, or trading.
The main body of the text is Spence's first attempt at combining his economic plan with a fully worked out political system, the radical but abandoned French constitution of 1793. Like the contemporary French Conspiracy of the Equals Spence thought the constitution of 1793 was a basis for a political equality which had little meaning without economic and social equality; like the Equals, he believed there should be 'No more individual property in land: the land belongs to no one. We demand, we want, the common enjoyment of the fruits of the land: the fruits belong to all'. Unlike the Equals Spence also wanted to resist centralization: the land would be shared at parish level, there would be no central direction of labour, and safeguards would be added to the constitution to block dictatorship. Spence also made it clear that his revised Constitution would be universal, and not specific to Britain or France: the name of the Republic is replaced throughout with asterisks.
The main changes Spence made to the 1793 constitution were:
- Asserting common property in land as a natural right, and so removing any property rights over land, including sale (Rights of Man, clauses 2, 3, 5, 20, 22; Constitution, clause 9)
- Making the parish, not just the individual, the basis of the constitution (Constitution clauses 2, 6, 7, 14 - 18, 21, 22)
- Removing the ability of the upper levels of government to levy taxes other than a land tax based on parish land holdings, and adding a universal income derived from the land tax (Rights of Man clauses 6, 24, Constitution clauses 49, 95, 96)
- Building in safeguards against arbitrary acts of government: Spence restored the 5th clause of the 1789 Declaration of the Rights of Man (Rights of Man clause 11), stating that 'no-one can be forced to do that which the law does not order'; strengthened clause 15 (the right to resist government acts not based in law becomes a duty); removed constitutional clauses (34-6 in the French original), which allowed for extraordinary assemblies with the ability to override the regular assemblies; and added clauses 112-113 limiting the power of the constituent assembly in relation to the parishes.