At first he planned a history of the Middle Ages, but by 1851 he had decided in favour of a history of civilization. The next six years were occupied in writing, altering and revising the first volume, which appeared in June 1857. It made its author a literary and social celebrity. On March 19, 1858 he delivered a public lecture at the Royal Institution (the only one he ever gave) on the Influence of Women on the Progress of Knowledge, which was published in Fraser's Magazine for April 1858, and reprinted in the first volume of the Miscellaneous and Posthumous Works.

On April 1, 1859, his mother died. It was under the immediate impression of his loss that he concluded a review he was writing of John Stuart Mill's Essay on Liberty with an argument for immortality, based on the yearning of the affections to regain communion with the beloved dead -- on the impossibility of standing up and living, if we believed the separation were final. The review appeared in Fraser's Magazine, and is to be found also in the Miscellaneous and Posthumous Works (1872).

The second volume of Buckle's history was published in May 1861. Soon afterwards, he left England to travel for the sake of his health. He spent the winter of 1861-2 in Egypt, from which he went over the deserts of Sinai and of Edom to Syria, reaching Jerusalem on April 19, 1862. After eleven days, he set out for Europe by Beirut, but at Nazareth he was attacked by fever; and he later died at Damascus.

Buckle's fame rests wholly on his History of Civilization in England. It is a gigantic unfinished introduction, of which the plan was, first to state the general principles of the author's method and the general laws which govern the course of human progress; and secondly, to exemplify these principles and laws through the histories of certain nations characterized by prominent and peculiar features,--Spain and Scotland, the United States and Germany. Its chief ideas are:

• That, owing partly to the want of ability in historians, and partly to the complexity of social phenomena, extremely little had as yet been done towards discovering the principles which govern the character and destiny of nations, or, in other words, towards establishing a science of history
• That, while the theological dogma of predestination is a barren. hypothesis beyond the province of knowledge, and the metaphysical dogma of free will rests on an erroneous belief in the infallibility of consciousness, it is proved by science, and especially by statistics, that human actions are governed by laws as fixed and regular as those which rule in the physical world
• That climate, soil, food, and the aspects of nature are the primary causes of intellectual progress,--the first three indirectly, through determining the accumulation and distribution of wealth, and the last by directly influencing the accumulation and distribution of thought, the imagination being stimulated and the understanding subdued when the phenomena of the external world are sublime and terrible, the understanding being emboldened and the imagination curbed when they are small and feeble
• That the great division between European and non-European civilization turns on the fact that in Europe man is stronger than nature, and that elsewhere nature is stronger than man, the consequence of which is that in Europe alone has man subdued nature to his service. That the advance of European civilization is characterized by a continually diminishing influence of physical laws, and a continually increasing influence of mental laws,
• That the mental laws which regulate the progress of society cannot be discovered by the metaphysical method, that is, by the introspective study of the individual mind, but only by such a comprehensive survey of facts as will enable us to eliminate disturbances, that is, by the method of averages
• That human progress has been due, not to moral agencies, which are stationary, and which balance one another in such a manner that their influence is unfelt over any long period, but to intellectual activity, which has been constantly varying and advancing: "The actions of individuals are greatly affected by their moral feelings and passions; but these being antagonistic to the passions and feelings of other individuals, are balanced by them, so that their effect is, in the great average of human affairs, nowhere to be seen, and the total actions of mankind, considered as a whole, are left to be regulated by the total knowledge of which mankind is possessed"
• That individual efforts are insignificant in the great mass of human affairs, and that great men, although they exist, and must “at present” be looked upon as disturbing forces, are merely the creatures of the age to which they belong
• That religion, literature and government are, at the best, the products and not the causes of civilization
• That the progress of civilization varies directly as "scepticism," the disposition to doubt and to investigate, and inversely as "credulity" or "the protective spirit," a disposition to maintain, without examination, established beliefs and practices.

Buckle either could not or would not define the general concepts with which he worked, such as "civilization", "history", "science", "law", "scepticism", and "protective spirit"; therefore his arguments are often fallacies. The looseness of his statements and the rashness of his inferences regarding statistical averages make him "the enfant terrible of moral statisticians". He brought a vast amount of information from the most varied and distant sources to confirm his opinions, and the abundance of his materials never perplexed or burdened him, but there is little well-conducted historical argument in his work. He sometimes altered and contorted the facts; he often simplified problems; he had certain favourite opinions. On the other hand, many of his ideas have passed into the common literary stock, and have been more precisely elaborated by later writers on sociology and history.