"Once, Dirac asked me whether I thought geometrically or algebraically? I said I did not know what he meant, could he tell me how he, himself, thought. He said his thinking was geometrical. I was taken aback by this because Dirac, with his transformation theory, represented for my generation the algebraic movement in physics par excellence. So, I said: 'I still don't understand.' He said: 'I will ask you a question. How do you picture de Sitter space?' I said, 'I write down the metric and then think about the structure of the terms in the expression.' He said, 'Precisely as I thought. You think algebraically, as most people from the Indian sub-continent do. I picture, without effort, the de Sitter space as a four-dimensional surface in a five-dimensional space.' (Kursunoglu 1990) Dirac's hidden geometry: what about the Hamiltonian?