There is not one definition of rationalism because it means so many different things. The Rationalists believe that knowledge is gained a priori or independently of experience. You know that 4 + 3 = 7, and that this won’t change wherever or you go to another country or to the moon. Knowledge of the world is gained through rational intuition (clear and distinct idea) and reasoning & understanding. A priori knowledge can be a hundred percent certain and is necessarily true.
A priori can be divided into four types: Prior to experience, which means that you have the knowledge before any experience. This is innate knowledge. Second and third ones are independent of experience and experience is irrelevant to a priori concepts or knowledge. An example of these is that you know that it can’t rain and not rain at the same time. The last one is that experience can’t justify a priori knowledge claims. This means that for a priori knowledge, you need more than experience. This leads to reasoning and understanding.
We can get a priori knowledge in three different ways. The first one is that the knowledge already could be in our minds at the mind’s inception, for instance the Forms, which is Descartes’ idea of God. This goes back to the first way of a priori: Prior to experience. The second one is intuition, which is the term we use when something is just obvious and we can’t explain how we know. Here we can use the same example as on second and third way of a priori: It can’t rain and not rain at the same time. The last way we can get a priori knowledge is through reasoning. You know that all humans are mortal and that you are a human. Therefore, through reasoning, you know that you are mortal.
In rationalism, reasoning and understanding is more important than the senses to the establishment of knowledge. Sense experience is an incoming visual, aural, touch,