Radical fictionism (or fictionalism) is of course the doctrine that all discourse is Fictive, so that there is no truth of any kind — mathematical, factual, or other. Like other epistemological doctrines, fictionism has old roots. One of them is skepticism ("Nothing can be known."), another nominalism ("There are no concepts: there are only things and names of things."). However, fictionism only attained adulthood in pragmatism ("Ultimately only action counts."). And it flowered in Vaihinger's monumental book Die Philosophie des als ob of 1911, which owed much to Kant, Lange, and Nietzsche.