1) There is a God.
2) Basic physics, in particular, the First and Second Laws of Thermodynamics.
The First Law of Thermodynamics states that matter and energy cannot be created or destroyed; only changed in form. The Second Law of Thermodynamics states that all matter and energy degenerates toward disorder. Both are natural laws. We have never found any exceptions to either of these two observations, thus the term “law”.
Because of the Second Law, we know that the universe did not always exist. If it had, everything would be at the same temperature near absolute zero, and you wouldn’t even be reading this. Since it didn’t always exist, that means there was a time when it didn’t exist, and then it began to exist. But that is a violation of the First Law. Any violation of natural law, by definition involves the supernatural (i.e. God).
3) Probably Spock whom I first saw on TV when I was about six years old, in particular, his emphasis on logic. Later I read a good book called "Logic" when I was in the seventh grade, that explained things even further. I got so good at it, that in college, I took "Introduction to Logic" as a required humanities course and scored the highest grade in the class. I loved it, and still do.
4) Buy any book on physics and you'll learn about the first and second laws of thermodynamics. You may also want to buy a book on logic; it will cover syllogisms and deduction.