To try to prove its existence, Descartes first begins with the doctrine of ideas. Which mainly reveals the nature that we have, because thinking about things is a thought. However, these thoughts are divided into categories. One category is what you think about and the other is how you think. The category about what you think about mainly consists of plans, images, feelings and emotions. The most complex category is that of our way of thinking since it is divided into subcategories: understanding, wanting and imagining. Descartes then deduces that if he has an idea, then this idea must therefore exist at least in ideas, not necessarily as an independent mind.