I think, therefore I am!!

Western philosophy in the 17th and 18th century was divided between British empiricism and continental nationalism. The Greeks were all about the thinking about how do we know what we know. Plato insisted it is knowledge preserved from a previous life. Locke believed that this knowledge was gained through experience. Empiracists believe the only source of knowledge is your senses, rationalists believe that you know things by figuring things out yourself.
Metaphysics:
Metaphysics believe that matter would still exist even if there is nothing there to percieve it, this brings about the classic scenario of "If a tree falls in the forrest and there's noone there to hear it, would it make a sound?". In my opinion it will, because there will never be absolutely nothing there to hear the falling tree. Idealism is the opposite, they believe that when objects are not being percieved they cease to exist, they also deny the existence of matter, and believe that everything is ideas.
"What I am aware of when i look at a chair is not the chair but how the table looks to me - it is the effect it produces in my mind when i look at it" - Berkely.
Rene Descartes:
Descartes opposed Aristotelianism and the traditional university education that was available at the time. He fought in many wars hoping that the action would give him insight, however, when this failed he embarked on a search for true knowledge. He did this by picturing a table in his mind, of which he cleared any ideas that he had in his mind and put back only those things which he knew to be absolutely true. The only rule that he believed worthy of the table were the rules of geometry becaue he believed that these would always be true, no matter what, even if there is noone there to percieve it. This led to the creation of the Cogito, which is "I think therefore I am", this is because in order to understand geometry he must be able to think. He dismissed any knowledge on the grounds of doubt. For example, you once believed in Santa (sorry those who still believe) and therefore what other crap will you believe? The way Descartes saw it was that you should doubt everything but the existence of God. This is known as the Descartes method. Since your senses are something that can decieve you, you should assume that some of what you can see is worthy of doubt. Cartesian philosophy contains 3 realms, mind/soul, matter and God. The first 2 are created substances while the third is the uncreated substance. Descartes epistemology sets off idealism, the thought of the idea of a perfect creation, but how could he have thought of such a thing? This thought of God proves the presence of God  - and God is perfect, therefore his senses wouldnt mislead him.
The Ontological Argument:
Descartes needed it to prevent the Cogito collapsing into solipismm. Kant says that existence is a neccesary condition for thought, not a result of thought. The problem with the dualist point of view is how the two substances interact. Descartes thought they communicatted at a specific point in the brain, which is rejected by materialists, who see matter as fundamental. Accounting for consciousness is a hard problem with this point of view though - described as the "hard problem"- how does subjective experience (heat, love, hate) arrise from the brain?
This is mainly about Descartes, expect Spinoza and Liebniz soon