great chain of being
The great chain of being is a doctrine, expounded by John Locke and others, according to which there is a complete continuum of existence from the lowest life-forms to human beings to extraterrestrial creatures with intellectual and sensory powers far greater than our own. Some saw this full spectrum of life as a necessary manifestation of God's omnipotence and it was often extended to include degrees of spiritual advancement. For example, it was commonly believed that other planets might be the home of angels or similar creatures that had progressed further along the road to divinity. In some cases, this belief was linked to that of the transmigration of souls. The great chain of being was one of a number of philosophical or theological arguments put forward, from the 17th century onward, in support of pluralism.