Passage (Thomas Babington Macaulay, "Milton," 1825, continued from his argument that poetry declines as civilisation advances): "But it is not thus with music, with painting, or with sculpture. Still less is it thus with poetry. The progress of refinement rarely supplies these arts with better objects of imitation. It may indeed improve the instruments which are necessary to the mechanical operations of the musician, the sculptor, and the painter. But language, the machine of the poet, is best fitted for his purpose in its rudest state. Nations, like individuals, first perceive, and then abstract. They advance from particular images to general terms. Hence the vocabulary of an enlightened society is philosophical, that of a half-civilised people is poetical. This change in the language of men is partly the cause and partly the effect of a corresponding change in the nature of their intellectual operations, of a change by which science gains and poetry loses. Generalisation is necessary to the advancement of knowledge; but particularity is indispensable to the creations of the imagination. In proportion as men know more and think more, they look less at individuals and more at classes. They therefore make better theories and worse poems." What is the central argument made in this passage?