During the 2014 Greer-Heard Forum, theoretical physicist and Caltech professor Sean Carroll and Christian apologist William Lane Craig discussed the question of whether modern cosmological understanding has theistic implications (watch the video). Craig claimed that it did. Carroll countered with alternate perspectives that offered other interpretations. Among a list of reasons supporting his view that theism was a "failed hypothesis," Carroll made the assertion that if theism were true, all people would hold the same religious beliefs and interpret spiritual experiences in the same way. Carroll explained that the diverse array of different religions made it seem probable—at least from his perspective—that there was no spiritual reality.
This assumption rests on a notion that all people who experience a phenomenon ought to respond and ascribe meaning to it in uniform ways. I'd like to examine an analogy based on electromagnetic radiation. Have human encounters with this force of nature resulted in standardized accounts of the experiences and universal consensus regarding meaning?
According to what physicists currently report, electromagnetic radiation comprises units of energy that are carried in packages called photons. Photons travel in waves, and the length of the wave (measured from peak to peak or from trough to trough) is significant. Possible wave lengths span an enormous size range. On the short end of the scale, gamma rays are measured in picometers (trillionths of meters). Radio waves span a range from millimeters (thousandths of meters) to kilometers (thousands of meters). At the long end of the scale, extremely low frequency waves are measured in megameters (millions of meters). Visible light falls into a narrow band from approximately 380 nm (nanometers, billionths of meters) to about 700 nm.
People see visible light because human anatomy is sensitive to it—not because it is fundamentally different from electromagnetic radiation at other wavelengths. Wavelengths just a little shorter than visible light fall in the ultraviolet part of the spectrum. They are invisible. Wavelengths just a little bit longer than visible light fall into the infrared part of the spectrum. They are also invisible (unless you get technological assistance from a device such as a pair of night vision goggles).
Visible light has no inherent color of its own. The perception of color occurs when human biology interacts with specific wavelengths of electromagnetic radiation. There are two kinds of cells within the eye involved in this process. They are called rods and cones, and they respond in different ways. The rods work best in low light conditions. They offer information to the brain in black and white and shades of grey. The cones require more light. There are three distinct kinds of cones. One kind is sensitive to the wavelength identified as red, one to green, and one to blue. There are seven million cones in each eye, and their coordinated output delivers information that the brain interprets as millions of different colors.
With this background information, let's return to our earlier question and consider whether human cultures have indeed identified colors in a standardized way and if a universal consensus regarding their meanings exists. After all, the qualities of the electromagnetic spectrum are precisely known and human optical biology is fairly uniform (with some leeway attributed to genetic and physical disorders), so the resultant interactions ought to be rather homogeneous. In fact, they are not.
Different cultures have different ways of categorizing color. Linguists have noted that some languages do not differentiate between blue and green. Some do not differentiate between brown and purple. In some languages, texture or other attributes of a surface are considered to be part of its color. And even within a group of people who all speak the same language, the boundaries between colors may be interpreted differently.
Meanings associated with colors also vary. In modern times and in many western countries, for example, a bride traditionally wears white (for purity). This was not true historically. Furthermore, in China, the traditional color for a bride's dress is red (for luck). And, Islamic brides wear a variety of bright colors, such as green (for luck) and yellow (to ward off evil).
Other important symbols and life events feature an arbitrary arrangement of specific colors. In modern times black is worn to symbolize mourning—except when it isn't. In India, the preferred color for mourning is white, and in some Asian cultures funeral etiquette requires blue or red. Which color combination stirs a patriot's heart? Well, it depends on the nation. And if you poll a large number of people will they say yellow means warmth, happiness, or jealousy?
Furthermore, a vast difference of opinion exists regarding favorite colors.
Another interesting point is that although science has been able to determine that people learn to call the color produced at a certain wavelength by a specific name, the question as to whether they are experiencing an identical perception remains open. That is, two people can look at a clear sky and agree that the color is called blue. If each could step inside the brain of the other, however, they might discover that their perceptions of blue differed, perhaps considerably.
This kind of diversity of interpretation actually pervades the human experience. For just one other brief example, consider music. Music involves the way human ears interact with sound waves. Individual notes have mathematical relationships with other notes, and yet societies have developed numerous ways of arranging them into scales. Scales with different numbers of pitches include pentatonic, heptatonic, and octatonic, and scales with different kinds of intervals between pitches include diatonic and chromatic. Furthermore, the wide assortment of methods for arranging musical notes is just the merest beginning of the range of ways in which music is experienced, expressed, and given meaning.
With such great dissimilarity in how people respond to manifestations of phenomena such as color and music, perhaps naturalists might begin to doubt the existence of the underlying phenomena. They don't, of course, so the existence of a similar diversity of interpretation within the spiritual realm seems to be insufficient grounds for denying its existence. It may be more accurate to presume that diversity of interpretation is a fundamental manifestation of the human experience in all realms.
Carroll didn't rest his argument on just this one point, however. He focused on the aggregate effect of a myriad of reasons. I'll discuss some of the others next.