A conceptual framework is an analytical tool with several variations and contexts. It is used to make conceptual distinctions and organize ideas. Strong conceptual frameworks capture something real and do this in a way that is easy to remember and apply. Isaiah Berlin used the metaphor of a “Fox” and a “Hedgehog” to make conceptual distinctions in how important philosophers and authors view the world. Berlin describes hedgehogs as those who use a single idea or organizing principle to view the world (examples given include Dante, Pascal, Dostoevsky, Plato, Ibsen and Hegel). Foxes, on the other hand, incorporate a type of pluralism and view the world through multiple, sometimes conflicting, lenses (examples include Goethe, Joyce, Shakespeare, Aristotle, Herodotus, Molière, Anderson, Balzac). Economists use the conceptual framework of “supply” and “demand” to distinguish between the behavior and incentive systems of firms and consumers. Like many conceptual frameworks, supply and demand can be presented through visual or graphical representations (see Demand curve).