Throughout history philosophers have influenced each other immensely. Sometimes present philosophers will agree with past philosophies and build on them. However, it is also common for present philosophers to criticize past philosophies. Two strongly differing arguments is John Locke and George Berkeley's views of existence.
John Locke believed strongly in the idea that secondary qualities exist only in the mind, leaving the primary qualities in the things themselves. Primary qualities exist in the object and are not dependent on the mind. Secondary qualities are inside the mind but exist independently. Certain qualities of a object has the power to create an experience in the mind. These messages of experience are written on the "blank tablet", or mind. Locke believes that this is where knowledge comes from.
George Berkeley has very different ideas of reality and existence. He varies from Locke by saying that even primary qualities exist only in the mind. Berkeley asked the question, "How do you know qualities exist?" He argued that one has no right to say primary qualities are more independent than secondary qualities of the mind. He believed this because he thought that all you experience or know are the ideas in your mind. These ideas or objects continue to exist through a mind that exists all the time- God. .
Criticism for these two philosophers or philosophies is abundant. Just a few of both Berkeley and Locke include that Berkeley's idea that all objects and ideas will always exist in God. This leads one to ask the question, "If God held these in existence when we are not looking, are they two separate existence's?" Clearly, one would look logically at the situation and say that there is only one existence of an object or idea. Berkeley fails to explain how there could be two separate existence's of one thing. Similarly, it can be argued that Locke is mislead in his thinking by the fact that his ideas of primary and secondary qualities is questionable.