One philosopher argued nothing exists unless something perceives it

George Berkeley claimed that objects have no existence independent of being perceived — 'to be is to be perceived.' A tree in an empty forest doesn't quietly sit there unobserved, on his view; it either continues to be perceived by some mind, or it doesn't exist at all in that moment. He offered it as a solution to scepticism about the external world, not a denial of reality itself.

— George Berkeley, A Treatise Concerning the Principles of Human Knowledge — 1710