Brain and mind in the 'long' eighteenth century

How should the 'long' eighteenth century be defined? January 1, 1700 and December 31, 1799 are quite arbitrary dates. Why should they be chosen to segment our history rather than more significant periods of time, periods which have a coherent content, or are marked, perhaps, by the working out of a theme? Students of English literature sometimes take the long eighteenth century to extend from John Milton (Paradise Lost, 1667) to the passing of the first generation of Romantics (Keats (d. 1821), Shelley (d. 1822), Byron (d. 1824), Coleridge (d. 1834)). Students of British political history often take it to start with the accession of Charles II (the Restoration) in 1660 or, alternatively, the so-called Glorious Revolution of 1688 and to end with the great Reform Act of 1832. Others might choose different book ends. In the history of science and philosophy the terminus a quo is sometimes taken as the publication of Descartes' scientific philosophy or, in more Anglophone zones, the 1687 publication of Newton's Principia with its vision of a 'clockwork universe'. 'Nature and Nature's laws' as Alexander Pope enthused, 'lay hid in Night: God said, Let Newton be! and all was light!'.