Existence of God
God is a spirit which cannot be seen, a being which cannot be touched. Yet despite not seeing Him, the evidence of His work is all around us in magnificent splendour.
This green flowery rock-built earth, the trees, the mountains, rivers, many-sounding seas;--that great deep sea of azure that swims overhead; the winds sweeping through it; the black cloud fashioning itself together, now pouring out fire, now hail and rain; what "is" it? This world, after all our science and sciences, is still a miracle; wonderful, inscrutable, "magical" and more, to whosoever will "think" of it.
This Universe, ah me--what could the wild man know of it; what can we yet know? What is it? God's Creation, the religious people answer; it is the Almighty God's!
Atheistic science babbles poorly of it, with scientific nomenclatures, experiments and what not, as if it were a poor dead thing, to be bottled up in Leyden jars and sold over counters: but the natural sense of man, in all times, if he will honestly apply his sense, proclaims it to be a living thing,--ah, an unspeakable, godlike thing; towards which the best attitude for us, after never so much science, is awe, devout prostration and humility of soul; worship if not in words, then in silence. (Thomas Carlyle)
Man
All around us is the handwriting of a Divine Author whose brilliance shines forth on each new day. Yet we do not even have to look outside ourselves to find examples of His handiwork. Let us look at ourselves, at man, who was created in the image of God.
But now if all things whatsoever that we look upon are emblems to us of the Highest God, I add that more so than any of them is man such an emblem. The essence of our being, the mystery in us that calls itself "I,"--ah, what words have we for such things?--is a breath of Heaven; the Highest Being reveals himself in man. This body, these faculties, this life of ours, is it not all as a vesture for that Unnamed? "There is but one Temple in the Universe," says the devout Novalis, "and that is the Body of Man."
We are the miracle of miracles,--the great inscrutable mystery of God. We cannot understand it, we know not how to speak of it; but we may feel and know, if we like, that it is verily so. (Thomas Carlyle)
Natural knowledge of God
Not only is the evidence of God's guiding hand demonstrated clearly to our senses, there is also something within each of us that tells us about the existence of this higher being. It is to this thought that men turn in times of sickness and death because it is the natural comfort which all men are inclined to follow.
That there exists in the human minds and indeed by natural instinct, some sense of Deity, we hold to be beyond dispute, since God himself, to prevent any man from pretending ignorance, has endued all men with some idea of his Godhead, the memory of which he constantly renews and occasionally enlarges, that all to a man being aware that there is a God, and that he is their Maker, may be condemned by their own conscience when they neither worship him nor consecrate their lives to his service.
Since, then, there never has been, from the very first, any quarter of the globe, any city, any household even, without religion, this amounts to a tacit confession, that a sense of Deity is inscribed on every heart.
Nay, even idolatry is ample evidence of this fact. For we know how reluctant man is to lower himself, in order to set other creatures above him. Therefore, when he chooses to worship wood and stone rather than be thought to have no God, it is evident how very strong this impression of a Deity must be; since it is more difficult to obliterate it from the mind of man, than to break down the feelings of his nature, - these certainly being broken down, when, in opposition to his natural haughtiness, he spontaneously humbles himself before the meanest object as an act of reverence to God. (John Calvin)
To believe in God is both rational and natural because it is based on the evidence of the world around us and the soul within us.