I make assertions about reality that you can't see, test, or dispute on any evidential premise. I am a Christian. I'm also an engineer, so it sometimes strikes me how differently I approach the two poles of my intellectual life (Jesus Christ and thermodynamics, in that order).
But consider the following:
He is the image of the invisible God, the firstborn of all creation. For by him all things were created, in heaven and on earth, visible and invisible, whether thrones or dominions or rulers or authorities—all things were created through him and for him. And he is before all things, and in him all things hold together. And he is the head of the body, the church. He is the beginning, the firstborn from the dead, that in everything he might be preeminent. For in him all the fullness of God was pleased to dwell, and through him to reconcile to himself all things, whether on earth or in heaven, making peace by the blood of his cross.
Jesus was God in the flesh - to see him was to see the father, insofar as that is a reasonable expression (as Jesus told his disciples - if you have seen me, you have seen the father). But this Jesus, the type, stamp, image, representation of the invisible God, was also instrumental in making all things, visible and invisible. Why is it strange to man that there is a world unseen, a very active world, full of creatures of God, either doing his will or opposing it - not unlike our visible, material world, eh?
But I received mercy for this reason, that in me, as the foremost, Jesus Christ might display his perfect patience as an example to those who were to believe in him for eternal life. To the King of the ages, immortal, invisible, the only God, be honor and glory forever and ever. Amen.
(1 Timothy 1:16-17)
The invisible God demands acknowledgment and praise here in this world. And this visible creation was made to echo his praises and sing of his power.
For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who by their unrighteousness suppress the truth. For what can be known about God is plain to them, because God has shown it to them. For his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made. So they are without excuse.
Paul makes the assertion that invisible attributes of the invisible God are nevertheless manifest to any man who opens his eyes on the world. Why? Because man is not limited in his faculties to the visible world. Man belongs to both worlds, seen and unseen, as body and soul comprise one man. Thus, the unseen world makes claims on man, whose eyes are limited, but who can yet perceive the power and divine nature of the Creator.
Now faith is the assurance of things hoped for, the conviction of things not seen. For by it the people of old received their commendation. By faith we understand that the universe was created by the word of God, so that what is seen was not made out of things that are visible.
Further, this visible world was summoned by the word of God to existence out of nothing. Faith is the hypostasis of things hoped for - the sublime multiphase colloid of our desires (if you look at an early usage of hypostasis in Greek medicine, it was what settled out on the bottom of bottles), the firm conviction of the deep reality of the invisible world and its transactions with our own, which include all aspects of salvation.
By faith Moses, when he was born, was hidden for three months by his parents, because they saw that the child was beautiful, and they were not afraid of the king's edict. By faith Moses, when he was grown up, refused to be called the son of Pharaoh's daughter, choosing rather to be mistreated with the people of God than to enjoy the fleeting pleasures of sin. He considered the reproach of Christ greater wealth than the treasures of Egypt, for he was looking to the reward. By faith he left Egypt, not being afraid of the anger of the king, for he endured as seeing him who is invisible. By faith he kept the Passover and sprinkled the blood, so that the Destroyer of the firstborn might not touch them.
The picture of Moses seeing the invisible God always, not just when he saw his back from the cleft rock, but an enduring vision of the invisible, this is what is called for. The world we see is made by God, but it is passing away, along with its desires, corrupted by Adam's sin. There will be a new heavens and a new earth, where elect men, redeemed by Jesus, will live body and soul with God. We are called to see the glory of God in the face of Jesus Christ, to hear his voice, not to harden our hearts, and to press on towards the upward calling of Christ. There is nothing more real than this invisible world, and there is nothing more important than the redemptive battle being waged in this visible world, not with weapons of the world, but with the armor of God and the sword of the Spirit and the Word. I need daily reminding to see the invisible, and it is a constant struggle to put more weight on what I cannot touch than on the simple things of life, work, food, and clothing. But to lean on the invisible God is to have an unshakeable foundation.