God, Subjective Idealism and Quantum Mechanics.
As is well known, so it needs no elaboration from me here, the only guarantee that there is a reality independent of our human minds in Berkeley's idealism is God - because such a reality would exist at all times in his mind. The fabled "tree in the quad" exists, even when no human is looking at it - even when no other sentient animal is looking at it - because God is doing so. There have been a number of attempts to remove God from the subjective idealist picture since Berkeley's time, of which a recent one is Helen Yetter-Chappell's 'Idealism Without God', Chapter 6, pp.66-81 in Tyron Goldschmidt and Kenneth L. Pearce, eds. (2017), Idealism. New Essays in Metaphysics , Oxford: Oxford University Press (OUP). Jonathan Head, in Chapter 3, 'Idealism in Fourfold Root', of Jonathan Head and Dennis Vanden Auweele, eds. (2016), Schopenhauer's Fourfold Root , Abingdon, Oxfordshire, England: Routledge (Taylor and Francis), argues that Schopenhauer was