Theory Maker is described as 'Free web app by Steve Powell for making any kind of causal diagram, i.e. a diagram which uses arrows to say what contributes to what. You make the diagrams just by typing the names of the elements (called variables) in a structured way into a (resizeable)' and is an website in the business & commerce category. There are more than 10 alternatives to Theory Maker, not only websites but also apps for a variety of platforms, including Mac, Windows, Linux and iPad apps. The best Theory Maker alternative is Penpot, which is both free and Open Source. Other great sites and apps similar to Theory Maker are PlantUML, Gephi, Graphviz and OmniGraffle.