• philosophical truths (such as the laws of logic);
• moral truths (murder is an evil act);
• historical truths (Columbus set sail in 1492 to discover a sea route to Asia);
• aesthetic truths (sunsets are beautiful)

So when it comes to providing reasons to believe that God exists, we need not limit ourselves to scientific evidence. We can appeal, for example, to the existence of objective morality (as C.S. Lewis did in Mere Christianity), to religious experience, or to Jesus’s resurrection from the dead. Nonetheless, there is powerful scientific evidence that points to God’s existence, and we’ll discuss two lines of this evidence below.

One final caveat before we proceed relates to the term proof. Merriam-Webster defines proof as evidence that “compels acceptance by the mind of a truth or a fact.” This is the everyday meaning of proof, in the sense of demonstrating something beyond any doubt. It’s important to note, however, that science is unable to provide this level of assurance. As the philosopher Karl Popper famously argued, scientific theories can’t ultimately be proven or confirmed, because other theories and observations may arise later that explain a phenomenon better. Thus, most leading scientists today recognize that scientific explanations are always provisional and may be modified or replaced in the future.

This is important to be aware of, because in the realm of science, we are always dealing with probabilities, rather than proof. Some piece of scientific evidence can point to God’s existence, and make it more probable, but scientific evidence can’t conclusively demonstrate that God exists. It’s simply beyond the purview of science to give us definitive proof about anything. So the evidence we’ll discuss below provides good and strong reasons to believe that God exists, but it can’t prove beyond any doubt that God exists. Science is incapable of reaching that high bar.

The Existence of the Universe

The most widely accepted account of how the universe came into existence is the Standard Big Bang model. Based on a number of different scientific observations, physicists have concluded that the universe sprang into existence out of nothing about 14 billion years ago. The most immediate question that comes to mind in light of this account is: Who or what caused the Big Bang?

Significantly, the standard model holds that all space, matter, energy, and time suddenly came into existence, from nothing, with the Big Bang. This means that whatever brought the Big Bang about is beyond space and time, immaterial, personal (this being made a decision to create), and unbelievably powerful. Of course, this is an excellent description of many of the attributes of God! Who else but God could have brought a universe into being?

Some scientists have proposed alternative scenarios seemingly designed to avoid an absolute beginning of the universe, but none have proven persuasive enough to replace the standard model. While scientific theories, as we’ve noted, are always subject to change, the Big Bang as currently understood certainly points to the existence of God.

The Fine-Tuning of the Universe

Although the fact that the universe exists at all is remarkable, another fascinating aspect of the universe is that it is fine tuned for the existence of life. Some examples include the following:

•The Strength of Gravity: The strength of gravity is determined by the gravitational constant. If gravity were significantly stronger, stars would burn out much faster, leaving less time for life to develop. On the other hand, if gravity were much weaker, stars might not form at all, preventing the creation of essential elements for life.

• The Cosmological Constant: This constant relates to the expansion speed of the universe. If it were just a little bit larger, the universe would have expanded too rapidly for galaxies and stars to form. Conversely, if it were smaller, the universe might have collapsed back on itself before life had a chance to emerge.

• The Strong Nuclear Force: This force holds together the protons and neutrons in an atom’s nucleus. If it were slightly weaker, protons and neutrons wouldn’t stick together, making complex atoms impossible. Without complex atoms, the chemical diversity necessary for life wouldn’t exist. If it were stronger, protons could potentially bind to each other more readily, which could lead to a universe without stable hydrogen, an essential element for life.

• The Size and Distance of the Earth from the Sun: Earth’s position in the solar system is in what scientists call the Goldilocks Zone, where it’s not too hot and not too cold, allowing for liquid water to exist on its surface. The size of Earth also ensures that it has the right gravity to retain an atmosphere suitable for life without being too strong to inhibit the mobility of organisms.

Those unfamiliar with the evidence for fine-tuning will sometimes claim that it’s a concept held only by Christians or theists. Yet scientists who claim no religious affiliation or are openly agnostic or atheist, acknowledge this fact about the universe. Fred Hoyle, an eminent physicist and agnostic, stated, “A commonsense interpretation of the facts suggests that a super intellect has monkeyed with physics, as well as chemistry and biology, and that there are no blind forces worth speaking about in nature.” In his book A Brief History of Time, the late Stephen Hawking wrote, “The remarkable fact is that the values of these numbers seem to have been very finely adjusted to make possible the development of life.” Physicist P.C.W. Davies, also religiously unaffiliated, insists that “the entire universe is balanced on a knife-edge, and would be total chaos if any of the natural ‘constants’ were off even slightly.”

The fine tuning of numerous constants and quantities of the universe is unexpected and mysterious if naturalism is true. But it makes perfect sense if Christianity is true, and God desired to create beings He could have a relationship with. Although acknowledging the provisional nature of science, there are good scientific reasons to believe that God exists, and these reasons seem to grow stronger the more we learn about the universe. For those interested in exploring the relationship between Christianity and science in greater detail, books by John C. Lennox and Stephen C. Meyer are a good place to begin.