Metaphysics
In the 15th century René Descartes thought there might be two different substances, mind and matter. This is a view called dualism. Other thinkers, like Immanuel Kant, thought that we cannot say anything about substance, as the only way we can talk about substance is through connections. To prove this, Kant used the sentence "This is a house". Kant thought that the meaning of the word house depended on how other people used houses, or how other houses looked like. This meant that meaning was all about connections, and that there is no meaning of "house" on its own. So Kant replaced the category of substance with relation in his metaphysical beliefs.