The Concrete Goals listed in the Communist Manifesto came from the practice of the Communist League; they were not theoretically derived. The general goal of socialism as something which could be proclaimed as a goal was also rooted in the practice of the European proletariat during the first half of the 19th-c. In fact, the Manifesto is NOT a theoretical document. For Marx's _theory_ you have to go to his Critique of Political economy: Theories of Surplus Value, Capital, Grudrisse.
Carroi
^^^^
Engels would seem to disagree that the Manifesto is not a theoretical document, a theory of history, here:
The 1872 German Edition
The Communist League, an international association of workers, which could of course be only a secret one, under conditions obtaining at the time, commissioned us, the undersigned, at the Congress held in London in November 1847, to write for publication a detailed _theoretical_ (emphasis added -CB) and practical programme for the Party. The practical programme in the Manifesto follows from the long historical materialist theory that proceeds it in the document.
and here
1. “This proposition,” I wrote in the preface to the English translation, “which, in my opinion, is destined to do for history what Darwin’ s _theory_ ( emphasis added -CB) has done for biology, we both of us, had been gradually approaching for some years before 1845. How far I had independently progressed towards it is best shown by my Conditions of the Working Class in England. But when I again met Marx at Brussels, in spring 1845, he had it already worked out and put it before me in terms almost as clear as those in which I have stated it here.” [Note by Engels to the German edition of 1890]
http://www.marxists.org/archive/marx/works/1848/communist-manifesto/preface.htm
Carrol's implication here and repeated refrain over the years that Marx and Engels held his view on the relationship between theory and practice is nonsense.