Does the universe exist primarily to serve as a home for us? This question cannot be answered with certainty. However, considerable evidence can be amassed in support of a “yes" answer. Consider the following facts.
Life is possible only because the universe is spatially flat and has been expanding and is continuing to expand at nearly the critical rate required to avoid collapse. If it had been expanding much faster, regions which had developed slightly higher than average densities would have continued to expand indefinitely and would not have formed stars and galaxies. If the universe had been expanding much slower, it would have collapsed long before the elements of life could have been generated in stars by nucleosynthesis. The numerical value of expansion rate is called the Hubble constant (H) and is currently 71 kilometers per second per megaparsec.
Life is possible only because the gravitational constant (G), the quantum of angular momentum (h), the speed of light (c) and the elementary unit of electrical charge (e) have the precise values required for the evolution of a very particular kind of universe. This universe contains short-lived, metal scattering blue stars and long-lived, evenly burning, slowly turning stars like the sun.
Life is possible only because of the delicate balance between the strong force that binds nuclei together and the enormous repulsive force between protons.
Life is possible only because the electromagnetic coupling constant and the ratio of electron mass (m) to proton mass (M) are precisely what are required to allow the formation of chemical compounds.
Life is possible only because the ratio of the strong force to the electromagnetic force has the precise value required to create a resonance between helium and beryllium nuclei allowing carbon-12 to form near the center of stars; carbon is the core element of all biochemical molecules.
Life is possible only because the weak-interaction coupling constant has precisely the proper value. If it were slightly smaller or larger, helium production would either be 100% or zero. In one case there would be no water, in the other an entirely variant stellar evolution.
Because H and c have the proper values to permit life, the characteristic length or "radius" of the universe (c/H) could not be significantly altered without precluding our existence. Also, since the universe is spatially flat, its density is essentially 3H2/8πG. The quantities H and G have the correct values to permit life; therefore, the density of the universe is what is required to permit our existence. Consequently, the universe contains no wasted space or matter even if life is unique to the surface of planet earth.
This list could be continued but it is already long enough to justify a conclusion: not one of the fundamental properties of the universe could be changed significantly without eliminating the possibility of life. Could this be what the Bible refers to when it says God's eternal power and divine nature are clearly evident in the things He has made (Rom 1:20)? Did a Supreme Being deliberately create the universe in such a way that the slightest change in any one of its properties would preclude our existence?
The only serious alternative offered, to date, is based on the idea that not just one but rather an enormously large ensemble of universes exists; each member of the ensemble is self-contained and unaffected by the rest. In this ensemble of universes, only our universe and those similar to ours contain living creatures. The rest are lifeless. The ensemble concept makes our universe just one of many and thereby avoids the need for us to occupy a special place. Aside from the fact that no supporting evidence exists for the ensemble concept, is it really more difficult to believe in God than in an ensemble of universes? (4,5,6)