Amy Kind in Aeon:

Philosophers have a love-hate relationship with the imagination. René Descartes, for one, disparaged it as ‘more of a hindrance than a help’ in answering the most profound questions about the nature of existence. Trying to imagine one’s way towards metaphysical truth, he wrote in Meditations on First Philosophy (1641), is as foolish as falling asleep in the hope of obtaining a clearer picture of the world through dreams. Yet Descartes also relied heavily on imagination in scientific and mathematical essays such as The World (1633), in which he tried to conjure up the details of the basic building blocks for structures such as humans, animals and machines. According to the philosopher Dennis Sepper at the University of Dallas, Descartes relied upon a kind of ‘biplanar’ imagination, pioneered by Plato, in which one level of reality could embody and display relations that existed on a different level, and vice versa. The Scottish philosopher David Hume was equally conflicted about the imagination – especially when compared with perception and memory. ‘When we remember any past event, the idea of it flows in upon the mind in a forcible manner,’ he wrote in A Treatise of Human Nature (1738-40). But imagined images and sensations, he continued, are ‘faint and languid, and cannot without difficulty be preserved by the mind steady and uniform for any considerable time’. However, Hume also claimed that humans are most free when they’re engaging in imagination. Perception can show us only the actual, he said, but imagination can go beyond that, to the realm of the maybe, the what-if and if-only. Indeed, ‘nothing we imagine is absolutely impossible,’ Hume said.

What’s behind this apparent tension at the heart of the imagination? Hume put his finger on it when he talked about how our facility for fantasy helps us to move beyond and change our present reality. One need only think of how Leonardo da Vinci’s fantastical flying machines paved the way for the Wright brothers, or how H G Wells’s novel The War of the Worlds (1898) inspired the first liquid-fuelled space rocket, to see the truth of this insight. But imagination is also restricted by the extent of our previous perceptions and experiences, Hume said. ‘Let us chase our imagination to the heavens, or to the utmost limits of the Universe; we never really advance a step beyond ourselves,’ he wrote.