In Descartes his first and second meditations he claims that all our beliefs can be doubted because our senses could simply be just an illusion, he goes on to say that although all our beliefs cannot be certain, because we think and experience, our minds must exist. Descartes argued that our ordinary experiences and views of the world cannot give us the kind of affirmed foundation on which all other knowledge and beliefs can be based. We are often dismayed to acknowledge that what we have learned is simply detriment, or that what our senses tell us is not certain. That should make us wonder about whether all the other things we believe might also be uncertain. So is there anything that we can know for certain without a doubt? We can doubt whether there is a physical world and whether we have a physical body. We can doubt whether our own reasoning can be trusted, so then what can we absolutely know for certain? Descartes gives an example that even if a higher power deceives us about all our other beliefs, there is one belief that we can be certain about, which is that we are thinking. Even to doubt this belief is proving that we are thinking. And since thinking cannot occur without there being something that does the thinking, this proves that we exist. When we think, it proves we have a mind, regardless of whether we have bodies. The body we experience as our own is not an essential part of our self because we can doubt its existence in a way that we cannot doubt the existence of our mind.Plato believed that reality was in the form of two separate worlds, he believed that something was an individual object, but could be put together into a larger group. For example there are multiple breeds of cats, but they all fall under a larger group, which is cats, or felines.