Key features of late nineteenth-and early twentieth-century British thought include analysis of the nature of liberty, keen interest in the role of the state in creating conditions for personal development, and belief either in perfectibility of human beings or in social progress, often in both. In spite of significant disagreements on these issues, the main representative thinkers of this period-here we focus on Herbert Spencer, T.H. Green, Bernard Bosanquet and L.T. Hobhouse-believed in systematic studies of human nature and society, drawing on a range of disciplines in humanities and natural sciences. Also, all of them believed in a link between morality and politics. Unlike the liberal political theorists of the second half of the twentieth century, these Victorian and Edwardian thinkers, all passionate in defending liberty, were not moral pluralists.