Philosophically there are only three reasons for existence or action: necessity, chance and design.

Everything in the physical realm has a beginning, an end and a cause.  Nothing physical is permanent.  Everything changes as a result of causes and are thus contingent on preceding events.  If everything has a cause, then an endless series of causes into the past is the result.  Of necessity, there must have been a beginning of the series of causes and effects.  But what started the series?  If everything in the physical universe has a cause, then something outside of the physical universe, by necessity, must have started the series of causes.  Why is there something instead of nothing?  Why does anything exist?  It must have been caused by something.  God or The Creator, by whatever name you wish to use, is the necessary first cause, the uncaused cause and everything else is contingent on it.   Therefore God is a necessary being that is eternal, having no cause, no beginning, and no end.

Since something outside the physical universe necessarily started the series of cause and effect, it also voids the assumption of the materialists that the physical universe is all there is; that the non-physical or spiritual only exists in our imagination. Of necessity, there must be a spiritual realm because, of necessity, something outside the physical must have started the series of causes.  This is a very old, but very valid argument for the necessary existence of God.  Atheists and materialists will dismiss it as “old news” but it is as valid today as it was when St. Thomas Aquinas included it in his Summa Theologica as one of the proofs of God.

If God started the whole thing, including existence, was it a singular act of creation which was then left to develop by itself without guidance? It can be argued that the present form of the universe is a matter of chance and only LOOKS designed.  It can also be argued that life came about by chance through some undefined “Life Principle” and only LOOKS designed.  Neither of these chance occurrences holds up to scientific or statistical scrutiny.  The physical universe is so finely tuned that if any of the fundamental forces or particles were changed by an infinitesimal amount, then stable galaxies, stars, planets and life would not have formed.

Life is a particularly complex and fine-tuned process and we are only just beginning to explore the workings of living creatures. For example, the probability of assembling one specific protein chain of 200 readily available amino acid units, from the 20 left-handed amino acids used in living systems is 1 in 20²⁰⁰.  To be plausible, the number of attempts must be in the ballpark of the odds.  If the universe is 13.7 billion years old, there have been 4.32 x 10¹⁷ seconds since it began. We would need to make 231.4 x 10¹⁸⁰ attempts each second since the beginning of the universe to make the random assembly of even this one specific protein plausible.

If we assume that life molecules were assembled on Earth, which is thought to be only 4.5 billion years old, and evidence of life was present 3.8 billion years ago, then the number of attempts per second rises to even more impossible levels. And that is just for one protein enzyme assembled from readily available units, excluding interfering molecules, and under the ideal conditions for assembly and preservation. Already we are seeing the extreme odds against a specific enzyme being produced. If we look at what it would take to produce by chance the thousands of different specific enzymes necessary for metabolism, the probability of random assembly of the correct mix would be (20²⁰⁰)³⁰⁰⁰ for a simple bacterium with 3,000 enzymes, or 1 in 10^780,000; that’s a 1 with 780,000 zeros after it. The terms impossible and miracle come to mind.

If chance is so improbable, then design or intent is a more plausible explanation for life and, indeed, the universe. The argument for intelligent design is that of impossibly high odds against the specified complexity we find.  A design necessarily implies a designer.  Not just any enzyme would perform the metabolic functions of even the simplest living being.  It must be a specific mix of specific enzymes with specific functions. That does not even address the formation of a living being, which is many orders of magnitude more complex than the formation of simple enzymes or structural proteins or DNA.

Conclusions:

1. God necessarily exists.
2. The spiritual realm really exists.
3. God has remained involved in the universe.