Unlike materialists positivists do not make any claims about a primary substance such as matter. They assume that we have data and that we interpret the data. The idea of a material world with three dimensions is, for positivists, just a good model to handle the experiences of everyday life. If astronomy has to deal with more complex data that cannot be handled consistently in such a model, they will have to think of a different model. Early 20th-century positivists like Ernst Mach said that the best model is the most "economical" model, that is the model we can use best in calculations and predictions.