A puppy is made through its parents. This series continues back and back. Stars are formed through matter that has been around for millions of years. All of the matter had to have been created at one point. Something has to have been around forever. This proof is good for people with a good understanding of science. It lays out what has to have for the creation of the universe and it doesn't in terms that people with good scientific background would be familiar with. St. Joe students would fall under this category.
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The simplest explanation of God, that could be given to uneducated people, is that billions of people have believed in God during human existence. All of these people can't be wrong. All of these people knew that life had meaning and that life was meant to be spent following God. The people who believed in God have found that God does exist through miracles, through people, and through unnatural coincidences. The easy example, someone is diagnosed with cancer. Most likely the patient is going to receive treatment. If the treatment doesn't work, the person is most certainly on their way to death. Lets say in this case the person is religious and has been praying to God and continues to pray for God. Eventually doctors find that the patient is cancer free. Since the treatment was a failure, the only explanation is that the person was saved through some divine hand. These types of situations show that there is a supreme being saving those who are loyal and respectful. People see God in others who are continually happy and there seems to be no rational reason for their happiness. Something must be at work putting the happiness into people. The same goes for coincidences that are lucky and unbelievable. Ultimately, something proves itself when we experience it firsthand, these experiences are found to be true by repetition or by others, and by their consistency with other experiences.