Is the concept of class war still valid?

‘Social stratification’ is the term used to describe systematic structures of inequality. In pre-industrial or traditional societies, inequalities and thus social stratification were widely held to be natural. Aristotle stated that ‘by nature’ there were free men and slaves, yet if inequalities are natural, Crompton suggests there be no need to explain them. The Hindu Caste system, as with the Feudal system of western Europe, both saw inequality as natural, yet it was not until the seventeenth century that, by virtue of their humanity, all humans were thought to be born equal….(short extract)