God the Father with His Spirit
So a common conclusion made today is that God must not exist seeing that we cannot see Him. This obviously is flawed reasoning for a number of reasons to begin with.
It can be scientifically stated that something doesn’t have to be visible in order to exist. After all, gases such as carbon, oxygen and nitrogen are invisible. So why not God? Saint Thomas Aquinas stated we can know God a posteriori, meaning we can know Him through His creation. So the Angelic Doctor mentioned various ways in which God’s existence can be proven.
He mentioned that truths about God “are not articles, but are preambles to the articles” and yet “can be known by natural reason” . Then he explains this by saying that “the existence of a cause is demonstrated from an effect, this effect takes the place of the definition of the cause in proof of the cause’s existence”. Science itself is based significantly on a posteriori arguments such as in regard to extraterrestrial life; we can logically conclude that life must exist on other planets because not only is the universe full of billions of galaxies with billions of planets, but many planets discovered have greenery or the ability to sustain life. In this case life on other planets is the effect of the cause which is the ability to sustain life (e.g. greenery and breathable gases).
As theists we can logically conclude there must be a God as the universe itself is a finite thing which was caused into existence, hence is the effect of a cause, that cause being an intelligent Being which is the single source of all finite things. Logically there cannot be an infinite number of beginnings as all creation starts somewhere and a conscious Being must be there to create it since no finite thing can create itself or be the cause of its own existence. For example I myself, a finite being born in time, cannot have been the cause of my own existence just as a car cannot be the cause of its own existence. Either way, a conscious being was there to be the cause of that other thing’s existence: for example, all of us are the product of natural sexual intercourse between one man and one woman and all cars are the product of men. Likewise all things in the universe, being finite — mainly meaning they have a beginning — must be created by a conscious Being who transcends time and space.
So what about naturalism and/or scientism? Naturalism and scientism are actually a handicap as they prevent the individual from going beyond questions which can be explained simply through what they can personally see. It enslaves the individual to abide simply by flawed and limited human reasoning to either conclude God does not exist or we cannot say for sure if He does. Even if a naturalist/scientist is presented with philosophical evidence that God exists, the person may likely reject it all with a statement like, “I can’t see Him” or “It must be solidly proven” and yet they cannot give any other logical reason to reject God’s existence. No, bringing up the sins of theists doesn’t work, especially since Atheists have committed grave sins too.
The problem with skeptics, particularly Atheists, is furthermore they seek to use the lack of evidence of God’s existence as if that somehow proves He cannot exist. But a lack of evidence does not disprove the existence of something. Only a contradiction can disprove something. Now before Atheists attempt to come up with some not-so-clever rebuttals I will say that paradoxes such as God’s omniscient, all-merciful and all-loving nature do not disprove God. I can have many conflicting personalities but that does not mean I don’t exist. It just means I am a complex person, as all of us are based on certain events, and that people simply can’t comprehend my mind. The same is with us who cannot comprehend God’s mind except in ways which He has revealed to us. A contradiction that could be used to disprove something is that it either exists or it does not exist, but it can’t both exist and not exist. Not only that but they cannot scientifically or philosophically disprove God’s existence and so His existence still stands.
 Summa Theologica I.2.2.