The theory of the indefinite progress of civilisation left Hume cold. There is little ground, he argued, to suppose that "the world" is eternal or incorruptible. It is probably mortal, and must therefore, with all things in it, have its infancy, youth, manhood, and old age; and man will share in these changes of state. We must then expect that the human species should, when the world is in the age of manhood, possess greater bodily and mental vigour, longer life, and a stronger inclination and power of generation. But it is impossible to determine when this stage is reached. For the gradual revolutions are too slow to be discernible in the short period known to us by history and tradition. Physically and in mental powers men have been pretty much the same in all known ages. The sciences and arts have flourished now and have again decayed, but when they reached the highest perfection among one people, the neighbouring peoples were perhaps wholly unacquainted with them. We are therefore uncertain whether at present man is advancing to his point of perfection or declining from it. [Footnote: Essay on the Populousness of Ancient Nations, ad init. ] The argument is somewhat surprising in an eighteenth century thinker like Hume, but it did not prevent him from recognising the superiority of modern to ancient civilisation. This superiority forms indeed the minor premiss in the general argument by which he confuted the commonly received opinion as to the populousness of ancient nations. He insisted on the improvements in art and industry, on the greater liberty and security enjoyed by modern men. "To one who considers coolly on the subject," he remarked, "it will appear that human nature in general really enjoys more liberty at present in the most arbitrary government of Europe than it ever did during the most flourishing period of ancient times." [Footnote: The justification of this statement was the abolition of slavery in Europe.] He discussed many of the problems of civilisation, especially the conditions in which the arts and sciences flourish, [Footnote: Essay on the Rise of Arts and Sciences.] and drew some general conclusions, but he was too sceptical to suppose that any general synthesis of history is possible, or that any considerable change for the better in the manners of mankind is likely to occur. [Footnote: Cf. Essay on the Idea of a Perfect Commonwealth, ad init.]