There are many ways to classify the myriad systems of belief about the nature of the world and humanity’s relationship to it, but for present purposes a very simple distinction between two broad categories will do. In the accompanying table, I include a third category for the sake of completeness. I will return to it briefly later, but will not characterize it further here.

I’ve characterized the first category as the Modern/Enlightenment perspective. Originating in the West during the period of the Enlightenment, it establishes personal happiness in this life as the fundamental goal of living. The Declaration of Independence, an Enlightenment document par excellence, codifies this idea in its listing of unalienable rights: “life, liberty, and the pursuit of happiness.”

The happiness to be achieved is not mere hedonic pleasure but something more akin to Aristotle’s eudaimonia, roughly translated as “flourishing.” The means to that end is to live in accordance with the best in human nature, which requires the exercise of reason in pursuit of one’s chosen goals. Reason proceeds ultimately from the evidence of our senses, which deliver to us the information we need to establish knowledge of the universe in which we find ourselves.

By careful observation and the exercise of our rational faculties, human beings can discover a set of basic moral principles that help us to make choices consistent with the goal of achieving long-term happiness and life-satisfaction. A passionate belief in the correctness of these principles motivates action in pursuit of that goal.

Contrast this set of beliefs with the Pre-Modern/Religious one. That differs strongly on two key dimensions. First, one’s ultimate goals are not to be found on the corporeal plane at all; life as we all know it is but the means to a transcendent end, to be realized only in a mystical realm where the non-material essence of the person—one’s soul—is immortal.

Living properly on the corporeal plane prepares one for acceptance into the loftier, more pleasant neighborhoods of the afterlife, whether these be conceived as abstract states of utter un-self-consciousness, as in the case of some Eastern systems, or as actual places where evil, pain, and suffering are unknown. Second, the means of knowing how to live life properly is to surrender one’s judgment to the inspirations of faith.

The idea is that—either directly, through a personal relationship with God or the Way, or indirectly, through the teachings of other, more enlightened people—one comes to understand God’s plan for one’s life. God is the authoritative source for the rules by which humans should live.

Physical reality and knowledge of it are but transient noise against the background of the truly significant spiritual realm to which all good souls aspire.Obviously these are not monolithic categories. Muslims and Buddhists share very few specific beliefs about the nature of the non-corporeal realm or the means to achieve access to it. Modernists are in greater accord about basic metaphysics and the means to knowledge but may be seriously at odds in matters of politics and morality.

I’ll return later to a discussion of how some of these ideological differences might make a psychological difference, but for now it is important to grasp the core distinctions between these two philosophical systems. For those who live a modern, secular life, reasoning one’s way to happiness in this life is the essence of humanity. For those who live a pre-modern, religious life, the ultimate goal of everlasting spiritual life can be attained only by surrendering concerns about this world to faith in the powers of otherworldly spirits.