In John Locke's philosophy of mind, all people are born with minds that are a blank slate. As such, we build up a body of knowledge through perceptions as we grow. In this way, all knowledge is received indirectly from outside of the human mind. In this, Locke distinguishes between primary and secondary perception. Primary perception gives an accurate impression of the qualities of an object, in terms of physical properties that can be measured, such as height, weight and width. Secondary perception on the other hand is dependent on the senses. Human sense organs differ from each other, and information such as color, taste and smell are therefore often perceived differently by different people. In this, Locke emphasizes that, while some perceived information may be regarded as reliable and some not, the object perceived can never fully be known in itself.
             George Berkeley takes Locke's philosophy a little further, questioning the actual existence of matter in terms of the human perception in terms of primary or secondary qualities alone. This doubt in the existence of matter is referred to as Idealism.
             The basis of Berkeley's philosophy is an attempt to reinstitute a belief in God in the field of philosophy. The reason for this is Berkeley's belief that Locke's doubt of the senses also casts doubt on the reliability of religious belief. To curb the skepticism and atheism encouraged by Locke's views, Berkeley calls upon a different view of the senses. In this, Berkeley takes the opposite view from Locke, that the experiences and powers of perception are not inherent in the object perceived, but rather in the perceiver. As such, the perceiver is the creator of perception, rather than the object. The object does not exist outside of perception; indeed, it is created by the power of our perception rather than the other way around. In this way the skeptical view of objects being different fr...