One of the traditional complaints about atheism is that it offers no grounds for believing that life is meaningful in any significant sense. Many old school atheists seemed to acknowledge this point. For example, Bertrand Russell grants that the eventual desolation guaranteed by naturalism is grounds for “unyielding despair,” and atheistic existentialists like Sartre and Camus recognized that without God life appears “absurd.” The new atheists are much more optimistic, insisting that life can be quite meaningful in the absence of God.
This makes me wonder whether life can really be as significant on an atheistic worldview as it is given the truth of theism and its correlative doctrine of an afterlife. Suppose we conceive of the overall significance of an action as relative to its total impact on what follows after, in terms of causal influence and consequences. Thus, for example, historians often refer to particular events, such as the assassination of Lincoln or the Treaty of Versailles as especially significant because of their impact on subsequent history. That seems reasonable enough. Now suppose we consider the significance of any individual human life along these lines as well, such that we recognize, say, that Martin Luther King’s life was especially significant because of all of the lives he impacted and continues to impact to this day.
Now with this understanding of life “significance” in hand, let’s compare the atheistic and theistic perspectives. Given atheism (or to be more precise, “naturalism”), all life on Earth will eventually perish, say 10,000 years from now, and whatever impact our lives have had will cease. I won’t say that the lives we led lose all significance as a consequence, but the significance of our lives will certainly be finite. However, given theism and the perpetual afterlife promised on this worldview, there is literally no end to the impact of our lives, for not only may earthly deeds continue to influence others forever but our on-going choices and actions in the afterlife (Heaven and/or the New Earth, given Christian theism) will be endless as well. Since there will be no end to our lives (at least for those who wind up in Heaven), there will be no limit to the significance of our lives or even individual actions, the effects of which may be felt and acknowledged for all eternity.
So, as we compare atheism and theism on this point, it turns out that the two worldviews could not contrast more sharply when it comes to providing grounds for the significance of human life. Given atheism, however long earthly history proceeds, in the end it will be finite and so will the significance of our lives. Given theism, on the other hand, the significance of our lives has no upper limit but approaches infinity. In other words, if theism is true, then the significance of our lives is immeasurably great, while in comparison, without God the significance of our lives is infinitesimally small. (I want to emphasize the comparative nature of my point here, for only relative to such a comparison could any degree of life significance be considered “infinitesimal.”)
So what does this mean? Is this evidence for the truth of theism? Not at all. On the contrary, there are no implications here with regard to which of these two worldviews is actually true. But what it does imply is that atheists who maintain that their lives can be just as significant (given the truth of their worldview) as those of theists (given the truth of theirs) are quite mistaken. In fact, the difference is infinitely great.