The question of whether there must be something eternal to set the universe in motion is a topic of philosophical and scientific inquiry. There are various perspectives on this matter, and different philosophical and religious traditions offer diverse explanations. I'll attempt to provide a general overview of some viewpoints.
Cosmological Arguments: Some philosophical arguments for the existence of an eternal or uncaused cause are rooted in cosmology. These arguments assert that everything in the universe has a cause, and therefore, there must be an initial cause or a first mover that set the universe in motion. This first cause is often considered eternal because it exists outside the framework of time and causality.
Theistic Perspectives: Many religious traditions propose the existence of an eternal and transcendent deity as the ultimate cause and sustainer of the universe. For example, in monotheistic religions like Christianity, Judaism, and Islam, God is often believed to be eternal and outside the constraints of time.
Scientific Theories: From a scientific standpoint, various cosmological models, such as the Big Bang theory, attempt to explain the origin of the universe. While these theories may not necessarily require an eternal entity to set the universe in motion, they do address the expansion and evolution of the universe from an initial state. However, scientific understanding of the origin of the universe is still an area of ongoing research and exploration.
The concept of something existing eternally can be challenging to grasp within our everyday understanding of time and causality. In traditional philosophical discussions, "eternal" often refers to existing outside of time or being timeless. Some philosophers and theologians propose that an eternal being, such as a deity, would not be subject to the limitations of temporal existence.
It's essential to acknowledge that questions about the nature of existence, causality, and eternity remain complex and may not have definitive answers. Different philosophical and religious traditions approach these questions from various perspectives, and the debate continues to be a subject of contemplation and exploration. As scientific understanding advances, our comprehension of these topics may continue to evolve.