The famous argument seems to logically explain the existance of God. However, the argument has a flaw. The Ontological Argument states: 1.I have an idea of supremely perfect being, i.e. a being having all perfections. 2.Necessary existence is a perfection. 3.Therefore, a supremely perfect being exists. The agrument does not define "perfect", which is a logically grey term. One could say that it is "lacking in any flaws". But then you must define "flaw" so as to not be logically grey as well. There are versions that use the term "great" in the following way: 1.There must exist a thing which greater than anything else. 2.God is defined as the greatest of all things. 3.God must exist. This is flawed because "great" is also a logically grey term. The Ontological Argument is dependent on logically grey terms. Without those terms, the argument cannot be made. Hence, there can be no argument made via logic to prove the existance of god which does not depend also on logically grey terms.