What is a republic ?

In which Paine discusses the "public thing"

“What is called a republic is not any particular form of government. It is wholly characteristical of the purport, matter or object for which government ought to be instituted, and on which it is to be employed, RES-PUBLICA, the public affairs, or the public good; or, literally translated, the public thing. It is a word of a good original, referring to what ought to be the character and business of government; and in this sense it is naturally opposed to the word monarchy, which has a base original signification. It means arbitrary power in an individual person; in the exercise of which, himself, and not the res-publica, is the object.

Every government that does not act on the principle of a Republic, or in other words, that does not make the res-publica its whole and sole object, is not a good government. Republican government is no other than government established and conducted for the interest of the public, as well individually as collectively. It is not necessarily connected with any particular form, but it most naturally associates with the representative form, as being best calculated to secure the end for which a nation is at the expense of supporting it.”

Thomas Paine
RIGHTS OF MAN, chapter 3.