Plato invented the subject of philosophy as we know it. Without the work of Plato, Western thought would indeed be unthinkable. Plato has exerted the greatest influence of any philosopher, in every era and in every philosophical field. Even those thinkers who rejected Plato's views were eventually forced to work on them. Platonism formed the basis and background of Christianity. It fueled many philosophical currents with its ideas from the beginning until today. Plato is perhaps the greatest philosopher of all time.