When we dream of a triangle, we experience a geometric shape with the measurable characteristics—angles and lengths—of a triangle. But the neural correlates of this dream in the physical brain are not triangular. So if all that exists is physicality, where in the physical world is the dream triangle? In this essay, Arthur Haswell not only elaborates rigorously on this thought experiment, but also anticipates and addresses various possible objections. The conclusion, he claims, is that the experiment demonstrates that there is more to reality than what we colloquially call ‘the physical.’