The importance of James Thomson's eighteenth-century poem The Seasons to Wordsworth's The Prelude has been systematically underestimated by critics, who take at face value Wordsworth's dismissals in his prose writings of Thomson's diction. In fact The Prelude contains a large number of allusions to and direct borrowings from The Seasons. Examining three of the most significant of these allusions, this essay argues that Wordsworth turned to Thomson in order to find a language that could express communion with the external, natural world, and specifically a communion that is mediated by the ‘bodily eyes’, with all their flaws and susceptibility to misapprehension. The poetic vision that is produced out of the eyes’ inaccurate vision is fundamentally ambivalent; mediation between the internal and external creates a space for the mind to exercise its creative and subjective power, but also reveals the mind's limitations. As well as assisting Wordsworth to articulate the mediated character of his encounters with nature, Thomson's language acts as a mediating presence itself, both facilitating and impeding Wordsworth's relationship with another great predecessor, Milton.