Historically, many rulers have assumed titles such as the son of God, the son of a god or the son of heaven. The term "son of God" is used in the Hebrew Bible as another way to refer to humans who have a special relationship with God. In Exodus, the nation of Israel is called God's firstborn son. Solomon is also called "son of God". Angels, just and pious men, and the kings of Israel are all called "sons of God." In the New Testament of the Christian Bible, "Son of God" is applied to Jesus on many occasions. On two occasions, Jesus is recognized as the Son of God by a voice which speaks from Heaven. Jesus explicitly and implicitly describes himself as the Son of God and he is also described as the Son of God by various individuals who appear in the New Testament. Jesus is called the "son of God," and followers of Jesus are called, "Christians." As applied to Jesus, the term is a reference to his role as the Messiah, or Christ, the King chosen by God. The contexts and ways in which Jesus' title, Son of God, means something more or something other than the title Messiah remain the subject of ongoing scholarly study and discussion. The term "Son of God" should not be confused with the term "God the Son" (), the second Person of the Trinity in Christian theology. The doctrine of the Trinity identifies Jesus as God the Son, identical in essence but distinct in person with regard to God the Father and God the Holy Spirit (the first and third Persons of the Trinity). Nontrinitarian Christians accept the application to Jesus of the term "Son of God", which is found in the New Testament. Rulers and imperial titles Throughout history, emperors and rulers ranging from the Western Zhou dynasty (c. 1000 BC) in China to Alexander the Great (c. 360 BC) to the Emperor of Japan (c. 600 AD) have assumed titles that reflect a filial relationship with deities. The title "Son of Heaven" i.e. 天子 (from 天 meaning sky/heaven/god and 子 meaning child) was first used in the Western Zhou dynasty (c. 1000 BC). It is mentioned in the Shijing book of songs, and reflected the Zhou belief that as Son of Heaven (and as its delegate) the Emperor of China was responsible for the well-being of the