An example is how Anselm believes that it is better for something to exist in both reality and understanding rather than pure understanding. This is true for many situations, but there are some occasions when it is better to have something that does not exist in reality, for example in the case of cancer. Imagine if cancer cells were just a figment of the mind understood by everyone, but yet cancer cells did not actually exist. However, everyone will agree that the best thing imaginable, i.e. a god, would be better in both understanding and reality. If a god is the best thing thinkable, he must exist both in reality and in understanding, because if he existed only in understanding he would not be the best thing thinkable. If a god did not exist at all, the concept would not exist in the understanding, but it does. Therefore, a god exists in both understanding and reality. Anselm's Ontological Argument does not necessarily prove the existence of a god, but, in fact, it proves the existence of the best thing imaginable, which is commonly believed to be