The human being has an intellect, will, heart which has a natural desire for God since he is immortal (will always exist).
“But no darkness of error or of sin can totally take away from man the light of God the Creator. In the depths of his heart there always remains a yearning for absolute truth and a thirst to attain full knowledge of it. This is eloquently proved by man's tireless search for knowledge in all fields. It is proved even more by his search for the meaning of life. The development of science and technology, this splendid testimony of the human capacity for understanding and for perseverance, does not free humanity from the obligation to ask the ultimate religious questions. Rather, it spurs us on to face the most painful and decisive of struggles, those of the heart and of the moral conscience.” (Veritatis Splendor #1)
Do you have free will?
Most people would say 'yes' to that question. How can you have free will if your body just follows the laws of science? In your brain are brain cells (neurons) which follow the law of physics and chemistry. If there is the right conditions it fire off an electrical signal. Without the right conditions it wont. Since this is based on chemistry it is automatic. One thing causes another to occur. We call this causality and it is automatic. (Now there are some who use some advanced physics concepts such as Heidegger's uncertainty principle to debate this, but properly understood any of these concepts can't deny human free will. See some of the links to the right to explore these deeper questions.) If our bodies are just causal then we can't have free will. But any rational person knows we do. So how can we have free will if my body on its own can't have free will?
We must have a soul that gives us free will. Once we realise this we can have start to develop a proper understanding of the human person. The study of the human person is called anthropology. All humans have a body and a soul. Without a body and a soul we are not fully human. Materialists believe we only have a body. Some scientists don't believe we have a soul. Science itself is not capable of exploring the reality of the soul since you can't experiment on a soul, nor detect it. So to believe you don't have a soul is not science, but can be labelled scientism which is a philosophy that believes science can answer questions it is incapable of answering such as whether God exists or whether you have a soul or not.
Really we have actually established two things, that you have a will and that it is free.
The human person having a soul, has the faculties of intellect and will. The human intellect seeks to know the truth. We don’t like 1 + 1 = 3. We know its wrong. We are happy with 1 + 1 = 2. Our intellect rejoices in the truth. My intellect has an infinite horizon. I am capable of having knowledge of infinity itself. I can imagine the whole universe. I can imagine things beyond the universe. I have the intellectual capacity for ultimate truth and I keep wondering about the causes, perfections and ends of things. My intellect will not be satisfied until I have attained to such knowledge. God is the infinite truth that my intellect is seeking. My intellect will ultimately be satisfied only in God himself.
The human will seeks whatever is good. A nice hot, yummy pizza is good. My will desires that yummy pizza because I know its good and so I want to eat it. My intellect is able to understand the pizza and so my will desires it. Through consumption I am satisfied. My will desires more and more good things. The more I have, the more I want. I want more. Nothing in this universe ultimately satisfies my will. I want the ultimate goodness. I want God. Only God can ultimately satisfy my will.
My heart is made for personal love. I want to know and enjoy the company of others. I am lonely on my own. I desire to know others and be known by them. Through their company I am aware that I learn about myself and can be truly myself. I become more myself through the friendship of others. I would like this to be complete to be fully known, to have a friendship where I can just be myself and hide nothing, just as nothing is hidden from me. I find that my friendships with others are limited and at times difficult. My heart yearns for a kind of infinite friendship and unconditional love.
God is this love that I yearn for, just as God is the infinite truth my intellect seeks is God and just as the infinite goodness that my will seeks is God. My heart yearns for God and as St. Augustine puts it, “our hearts are restless until they rest in you.” We have a natural desire for God which can only be fully fulfilled by him.
I am aware that my earthly existence will end, but I can’t conceive of not thinking since it is so intrinsic to me. My capacity for truth, goodness and God give me the sense that I will live on beyond death. Science can’t answer any questions beyond death. But my capacity for answers point to a reality that there is beyond death and my transcendent capacities of an intellect with an infinite horizon, a will for the ultimate good and a heart for total friendship points beyond this life to a fulfilment that must exist beyond death. God must be able to give that fulfilment, as scripture says, “Now we see but a poor reflection as in a mirror; then we shall see face to face. Now I know in part; then I shall know fully, even as I am fully known.” (1 Cor 13:12) This ultimate experience the Catholic Church calls the beatific vision, where our intellect will see God, our will will be ultimately satisfied by God, we will know God and be fully known by God in the most intimate friendship and we will experience heavenly bliss, “The beatific vision, in which God opens himself in an inexhaustible way to the elect, will be the ever-flowing well-spring of happiness, peace, and mutual communion.” (CCC 1045) But we have jumped ahead of ourselves.
The natural desire for God is expressed through our intellect which seeks ultimate truth, a will seeking the absolute good, and our heart which seeks unconditional love. Having established these aspects to the human person and recognising everyone desires these things, everyone therefore desires God, even though they may not acknowledge God in their life. It is human to have all these desires, but we can’t fulfil them by ourselves. I can’t just see God. I am finite and God is infinite. Therefore I have to wait upon God to act. Because I am a personal being, only through personal relationship can I be fulfilled.
The nature of human life is that man has a perishable body, but an immortal soul as one complete human person. Each human has an intellect that seeks truth, a will that seeks goodness and a heart that seeks love. The infinite horizon of the human mind means humans are open to the infinite and therefore religious by nature and so have a natural desire for God, who alone can fulfil humanity.
“two fundamental truths should be kept in mind: first, that man is called to live in truth and love; and second, that everyone finds fulfilment through the sincere gift of self.” (John Paul II, Letter to Families)
“Our hearts are restless until they rest in God” (St. Augustine)
“There is a God shaped vacuum in the heart of every man which cannot be filled by any created thing, but only God, the Creator, made known through Jesus.” Blaise Pascal.
"If I find in myself a desire which no experience in this world can satisfy, the most probable explanation is that I was made for another world." - C.S. Lewis