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Thomas Aquinas was a famous thinker who wanted to explain why God exists in a way everyone could understand, even if they didn’t believe in the Bible. In his book Summa Theologica, he came up with five reasons, or “proofs,” for God’s existence. These ideas are based on observing the world around us and using logic to figure out why things are the way they are.

  1. The Prime Mover

Aquinas said, “Everything that moves has to be moved by something else.” For example, if you see a ball rolling, you know something had to push it. Aquinas looked at the universe and saw everything moving—planets, stars, even the wind. He believed there had to be a “Prime Mover,” something that started all the motion but wasn’t moved by anything else. That Prime Mover, he argued, is God.

  1. The First Cause

This is like asking, “What caused everything to exist?” Aquinas said, “Everything has a cause.” For example, a tree grows because someone planted a seed, and the seed grew because of water and sunlight. But Aquinas argued there can’t be an endless chain of causes going back forever. At some point, there has to be a First Cause that caused everything else but wasn’t caused by anything. That First Cause, Aquinas said, is God.

  1. Possibility and Necessity

Aquinas noticed that everything in the world depends on something else to exist. For example, humans need oxygen to breathe, and plants need sunlight to grow. He argued that if everything depends on something else, there must be something that doesn’t depend on anything—something that exists on its own and always has. That “necessary being,” according to Aquinas, is God.

  1. Degrees of Perfection

Have you ever noticed how we compare things? We say one thing is better, bigger, or more beautiful than another. Aquinas said that if we recognize something as “better” or “more perfect,” there must be an ultimate standard of perfection. Imagine trying to measure the tallest mountain without knowing what the tallest possible height is. Aquinas argued that this ultimate perfection exists in God, who is the most perfect being.

  1. Intelligent Design

Aquinas looked at nature and saw that everything seems to work in a purposeful way. For example, the Earth orbits the Sun at just the right distance for life to exist, and birds instinctively know how to build nests. He believed this order and purpose didn’t happen by chance. Instead, it points to an intelligent designer who planned it all. That designer, Aquinas said, is God.

Thomas Aquinas wanted people to see that faith and reason go hand in hand. His five proofs give us logical ways to think about God’s existence. Whether it’s motion, causes, purpose, or perfection, Aquinas believed everything in the universe points to God. Even today, his ideas inspire people to think more deeply about the big questions of life.