"Much literature has been called forth by the Covenanting movement in Scotland, and my sole reason for adding another volume to the library of Covenanting history and biography is that one of the greatest of the Covenanting leaders has been allowed to sink into a quite unmerited oblivion. Alexander Shields, who was after the execution of James Renwick the acknowledged leader of the Cameronian remnant, was one of the most picturesque figures in the Scotland of his day... he lived dangerously and died young; and it is indeed strange that no biography of this remarkable man has yet been attempted... He was a man of thought, and he may with some justice be called 'the Cameronian philosopher,' for in his greatest work, 'A Hind Let Loose,' he expounded... the philosophy of what might be called Radical Calvinism... He is worthy to rank with Buchanan and Rutherford among the chief Scottish protagonists" concerning Calvinistic political theory.

Though MacPherson is exceedingly weak in expressing some points of the hard-edged Cameronianism of Shields the book is still useful for much of the information that it contains. It also helps set the context for Shield's masterful and revolutionary work A Hind Let Loose, a book easily in the class of Rutherford's famous Lex Rex.