Plato contended that all true knowledge is recollection. He stated that we all have innate knowledge that tells us about the things we experience in our world. This knowledge, Plato believed, was gained when the soul resided in the invisible realm, the realm of The Forms and The Good. Plato's theory of The Forms argued that everything in the natural world is representative of the ideal of that form. For example, a table is representative of the ideal form Table. The form is the perfect ideal on which the physical table is modeled. These forms do not exist in the natural world, as they are perfect, and there is nothing perfect in the natural world. Rather the forms exist in the invisible realm, the realm of The Good. When the soul resided in the invisible realm, it experienced these perfect forms and retained that knowledge. However, when the soul is born into the natural world, it forgets that knowledge. In this world, the soul has no experience of perfection, and, therefore, cannot remember the forms. Yet, when the soul is confronted with something resembling the forms, it recollects what it once knew. We call this learning, but Plato believed it is actually recollection. For example, when we see two sticks that are the same length, we say that they are equal. Yet, there is nothing in the natural world that shows us true equality. Therefore, we must have had knowledge of the idea of equality before we entered this world. When we see the two sticks of the same length, it triggers the recollection of the idea of equality. Hence, Plato argues that our soul, before it entered this world, had knowledge of the form of equality when it was a part of the invisible realm. Upon entering this world, this knowledge was forgotten and had to be recollected. Thus, all knowledge of the forms, such as equality, justice, etc. is recollected. However, in proving that what we call learning is actually recollection, Plato also proved that the soul is immortal.