John Locke was an empiricist philosopher that believed that all knowledge was derived from sense perception. Meaning all of our knowledge is obtained through the 5 senses. He believed that a concept or idea must be experienced in order to be deemed true. Things like God and eternity have not been experienced, so they would be labeled as a false conception.
Locke believed that everything learned by sense perception begins with simple sensations. Simple sensations are sensations that are perceived through individual senses. These simple sensations identify other simple sensations and combine to make one complex idea. For example, an apple is a complex idea made up of smaller ideas such as the color green, the taste and the smell.
Despite being an empiricist, Locke did have some rationalistic views. He believed that certain ethical principles applied to every human being. He also believed that God existed, but not because of faith, but because of human reason.