This work investigates the fundamental question of whether the evolution of language, specifically English, represents a form of progress toward greater efficiency and clarity. Otto Jespersen, a renowned Danish linguist, utilizes his extensive expertise in historical grammar and phonology to analyze the structural shifts in English over centuries. He argues that the transition from synthetic to analytic structures reflects a rational simplification that enhances the communicative utility of the language. By examining historical data and linguistic patterns, he constructs a framework that challenges the notion that language change is merely a process of decay.

Linguists and historians frequently cite this text as a foundational contribution to the study of language change and the history of the English language. Scholars often note the dense, scholarly prose and the rigorous empirical approach Jespersen applies to his linguistic theories.