1. Introduction to Philosophy Descartes’ First Meditation
The three main types of arguments for the existence of God:
cosmological (“first cause”)
the bare fact that there is a universe, that things exist
teleological (”design”)
the fact that many things in the universe have purpose or order
ontological
the idea/definition of “God”

2. Introduction to Philosophy Descartes’ First Meditation
ontological argument by Anselm of Canterbury (1078):
God is defined as "that than which nothing greater can be thought“
if the greatest possible being exists in the mind, it must also exist in reality. If it only exists in the mind, then an even greater being must be possible — one which exists both in the mind and in reality
Therefore, God exists

3. Introduction to Philosophy Descartes’ First Meditation
epistemology
noun PHILOSOPHY
the theory of knowledge, especially with regard to its methods, validity, and scope. Epistemology is the investigation of what distinguishes justified belief from opinion.

4. Introduction to Philosophy Descartes’ First Meditation
Idealism
Many idealists believe that knowledge is primarily (at least in some areas) innate—for example, in the form of concepts not derived from experience.
Empiricism
In philosophy, empiricism is generally a theory of knowledge focusing on the role of experience, especially experience based on perceptual observations by the senses. 
Rationalism
the doctrine that knowledge is acquired by reason without resort to experience 
Constructivism
Constructivism is a view in philosophy according to which all knowledge is a compilation of human-made constructions, not the neutral discovery of an objective truth. 

5. Introduction to Philosophy Descartes’ First Meditation

6. Introduction to Philosophy Descartes’ First Meditation
Rene Descartes
1596 – 1650 French
philosopher, mathematician, and scientist “father of modern western philosophy”

7. Introduction to Philosophy Descartes’ First Meditation
Meditation I: Concerning Those Things That Can Be Called into Doubt
Meditation II: Concerning the Nature of the Human Mind: That the mind is more known than the body
Meditation III: Concerning God, That He Exists
Meditation IV: Concerning the True and the False
Meditation V: Concerning the Essence of Material Things, and Again Concerning God, That He Exists
Meditation VI: Concerning the Existence of Material Things, and the Real Distinction between Mind and Body

8. Introduction to Philosophy Descartes’ First Meditation
The historical impact of the six meditations has been divided.
The first two meditations, which employed the skeptical methodic doubt and concluded that only the ego and its thoughts are indubitable, have had a huge impact in the history of philosophy.
They are often considered as epoch-making for modernity, and an unavoidable first step for any modern philosophical thinking.