Playing the Numbers: A Millennial Engineer's Probabilistic Approach to Believing in God

A core premise (perhaps the core premise) of religiosity is faith, which I define as “believing in things one cannot see or otherwise definitively prove.” Though faith is an essential component to any religious conversation, I’d like to set it aside for just a moment and focus instead on a pragmatic and logical way of thinking about religion.

The topic in question: “Does God exist?”—a question that has sparked divisive debate for millennia. Believers will present mountains of “evidence” while non-believers will correctly point out that such “evidence” cannot amount to “proof.”

Rather than pick my side and try to convince others of its relative merit, I take a different approach. Let’s look at the problem rationally, from a distance, by comparing the expected utility and implications of each option.

For the purposes of illustration, let’s simplify the spectrum of possibilities down into two distinct categories: either there is a God, or there is not. The primary end goal of most religions is to influence people to live according to a moral code, usually set forth by deity. So again, let’s boil the infinitely broad spectrum of lifestyle choices into two simple categories: to obey God’s moral code or to not obey God’s moral code.

For a visual aid, we plot our two dimensions onto an empty probability square.

Since the goal of most rational people is to maximize one’s own happiness, we’ll use a rough relative measure of happiness level for the values in our square.

The doctrines of most religions include some flavor of an afterlife, so we’ll also add a third dimension to our square: this life vs. the afterlife.

We’re ready to start filling out our diagram, starting with the left column. We might describe these cells as “the happiness level in both this life and the afterlife of people who obey God and who do not obey God, given God exists.”

“Happiness in this life” is difficult to measure. Though some research suggests that religiosity is directly correlated with increased happiness, health, and wealth, in my observation faithful people do not have a corner market on happiness or prosperity, and they certainly aren’t immune to the challenges of being human. Conversely, despite what many non-religious people believe, living free from the rigors of a religious lifestyle isn’t necessarily a path to greater happiness in the long run. To keep our estimates conservative, we’ll assume that the happiness level of both religious and non-religious people is approximately the same. We’ll mark this level as “average.”

The afterlife dimension of these cells is more straightforward. Most religions concur that obedience to God in this life warrants some sort of reward in the afterlife; and disobedience results in some form of diminished happiness, at least temporarily.

On to the right column. We will reuse our previously calculated “Average” happiness level for both obedient and non-obedient people for this life into this column. Since there is no God and presumably therefore no afterlife in these scenarios, we’ll put “N/A” for the afterlife values.

With our square filled in, we can now finish our analysis. Since the existence of God can neither be proven nor disproven (much to the chagrin of both believers and non-believers), we’ll naively assign an equal probability of 50% to both options. And in lieu of a more precise measure for happiness, we’ll make a simple assignment of 1, 2, and 3 to our rough levels.

Now we can calculate the expected value for happiness for the two lifestyle choices:

• Obey: 0.5 × (2 + 3) + 0.5 × 2 = 3.5
• Not obey: 0.5 × (2 + 1) + 0.5 × 2 = 2.5

Our simple analysis suggests that obedient people will have a larger expected happiness, and therefore the rational choice to maximize well-being is to live in accordance to God’s moral code.

Of course, life is infinitely more complex and our illustration may only serve as little more than a thought experiment, but a valid point still remains: banking life decisions on whether or not to live by a moral code solely on the existence or absence of God is an enormous bet and strictly a one-way ratchet in the sense that the upside is negligible with the potential for substantial downside.

As for me, I like my choices to be the opposite: negligible downside with the potential for infinite reward.