“Those who attribute everything to nature do indeed see these phenomena, but their only thought is that they exist. They simply say that nature has that effect. They say this because they turn their minds away from thoughts about the Divine; and when people who turn away from the Divine see astounding things in nature they cannot think about them rationally, much less spiritually. They think with their senses and in a material way. They think in nature, from nature, and not beyond it. The only difference between them and animals is that they have rational capability, meaning that they could understand if they wanted to.
“Those who are averse to thinking about the Divine and have therefore become mindlessly sense-oriented, fail to realize that their eyesight is so dull and limited to physical matter that it sees a mass of tiny insects as a single vague object, although in fact every single one of those insects has organs for sensing and moving. They are equipped with fibers and vessels, with tiny little hearts, windpipes that function like lungs, internal organs, and brains that have all been woven out of the finest substances in nature. Those structures respond to life at the lowest level; that life individually activates their most minuscule parts. Eyesight, then, is so dull that it sees many things, each of which has countless elements, as nothing more than a little blur; and yet sense-oriented people think and pass judgment on the basis of their eyesight. Obviously, then, their minds are dulled, and they are in darkness regarding what is spiritual.
“All of us, if we want to, can use phenomena in nature to support a belief in the Divine; and we do so when we think about God, about the omnipotence he displayed in creating the universe, and about his omnipresence in preserving the universe.
“For example, when we see the birds that fly in the sky we can reflect on the fact that each species of them knows its own food and where to find it, and recognizes its companions by sight and sound. In fact it knows which birds among all others are friendly and which are hostile. Birds know the mating of their kind; they pair off with a mate, they artfully arrange nests, and in them they lay their eggs and brood over them; they know how long to incubate them; and when the time comes they hatch their young, give them tender love, nurture them under their wings, and gather food and feed them, until the young come of age and can take on those tasks for themselves. All who are willing to think about a divine inflow through the spiritual world into the physical world can see that inflow from these examples. If they are willing, they can say in their hearts that such knowledge cannot be acquired from the sun through its heat and light. The sun, nature’s origin and essence, is nothing but a fire. The flow of heat and light from it is utterly dead. From this they can conclude that these phenomena are the result of divine inflow through the spiritual world into the outermost aspects of nature.
from True Christianity, Volume 1, Section 12