"I DON'T BELIEVE IN THE SPIRITUAL. I ONLY BELIEVE IN WHAT I CAN SEE."
If you pinch an inch around your waist, the fat you are squeezing around your fingers is not the same as it was last month. Your adipose tissue (fat cells) fills up with fat and empties out constantly so that all of it is exchanged every 3 weeks. You acquire a new stomach lining every 5 days (the innermost layer of stomach cells is exchanged in a matter of minutes as you digest food). Your skin is new every 5 weeks. Your skeleton, seemingly so solid and rigid, is entirely new every 3 months. In all, the flow of oxygen, carbon, hydrogen and nitrogen is so rapid that you could be renewed in a matter of weeks; it's only the heavier atoms such as iron, magnesium and copper that slow down the process. You appear to be the same outwardly, yet you are, in reality, like a building whose bricks are constantly being replaced by new ones. Every year, fully 98% of the total number of atoms in your body are replaced [this has been confirmed by radioisotope studies at the Oak Ridge laboratories, California, USA (Chopra, Perfect Health).]
"SO, WHAT'S YOUR POINT?"
From the above facts, we can therefore say that there is not one atom in our bodies that was part of us when we were 3 years old! Our body is like a river, constantly changing. There is, however, a feature of us which is not subject to the same changes: our spiritual soul. Our body will come and go, but our spiritual soul will never die. That is why we can say that we live forever. Right at this moment, we are composed of body and spiritual soul. The body is easy to see, we can feel it and can sense our surroundings with it, but our spiritual soul is invisible. Like the wind, we know it exists, yet we can't see it. We can see its effects but we can't see it. We can see the leaves rustle in the trees and we know that the wind is blowing, but we aren't seeing the wind, we are only seeing the effect it is having on the tree. We can think a thought, we can use that thought for good or bad, we can decide to act for good or bad. In all of these actions it was not the body that was used, rather it was the intellect (mind) and will (heart) of our spiritual soul. The body simply acts out what the spiritual soul makes it do (Sheed, Theology for Beginners).
So, there's more to us than meets the eye. It should therefore be less of a surprise to us that God, who is a Spirit, is also invisible in our daily lives. But, just because something is invisible to us does not mean that it doesn't exist. God really does exist and His existence can be backed up by pure logical reasoning and scientific evidence.
"WHERE'S YOUR EVIDENCE?"
The ordered design and incredibly exact fit of things in the universe proves that only God the Intelligent Designer could have created it all from nothing. The astonishing consistent intricacy of DNA in every single nucleus of every single human cell has an improbability of at least 10 to the power 78,000 of ever having arranged itself to such a high degree of detail in a purely random manner. The structure of haemoglobin in our blood has an improbability of at least 10 to the power 630. Such mathematical odds are stacked in favour of those who believe in an Intelligent Designer (God). The likelihood that life was created by random chance is about the same likelihood that a hurricane could blow through a junkyard and create a jumbo jet. [See Darwin's Black Box, by Michael Behe, for more evidence of Intelligent Design.]
"BUT EVEN IF GOD DOES EXIST, IT'S TOO HARD TO KNOW WHO HE IS."
Give God a break. What more does He need to do? He became human; but in doing so He had to pick some time in human history. And He picked the Middle East as the area in which He would live. And just because His choice of time and place for dwelling among us just so happens not to coincide with ours, that is not a good enough reason for not believing in Him. Being really human, He has only lived one life on Earth, so please, give Jesus a break. Those who doubt the existence of Jesus Christ have no difficulty accepting the existence of Julius Caesar, yet there is more historic evidence of Jesus. [See Jesus the Evidence by Ian Wilson.]
"HOW DO I KNOW GOD LOVES ME?"
Because He died for you. We would all still have a nagging doubt about His love for us if He had not died for us on the Cross; in doing so, by dying for each of us individually, He has given us proof that He loves us. Miracles and the Gospel are awesome, but the greatest sign of God's love for us is to look upon the Man who hangs on the Cross. His name is Jesus and He is God and He loves each of us individually more than anyone ever could.
* Please note that this text should be read in the context of the whole work and in recognition of the appropriate paragraphs of the Catechism of the Catholic Church highlighted in the index.