Descartes, René, Elizabeth Sanderson Haldane, and G. R. T. (George Robert Thomson) Ross. “Meditations: Excerpts.” In The Philosophical Works of Descartes. Cambridge : University Press, 1911; 1973. http://archive.org/details/isbn_052109416x.
In finding out what is true about the world, what should we trust? Should we trust what our senses tell us or what our intellects tell us? Look at this figure. It's called the Penrose triangle. Is what you're seeing possible? Could it really exist? Does your intellect tell you something different from what your senses tell you about this figure? Which one should you trust? Your senses or your intellect? Which answer would Descartes say is correct?
