The text revolves around the core philosophical ideas of the British empiricist philosopher George Berkeley, namely, 'to be is to be perceived.' The article elaborates on the background and purpose of Berkeley's theory, primarily to refute materialism and to avoid skepticism and atheism. It also explores the common misconceptions about Berkeley's theory, particularly how he ensures the continued existence of the external world through God's perception. Finally, the article presents several possible angles to refute Berkeley's theory and summarizes its significant influence on the development of subsequent philosophy.