November 18, 2009
Image source: tutornext.com
Yesterday we talked about asteroids, and the fact that “there’s no evidence for X” type claims are often made amidst the very evidence being denied. We also discussed the interesting truth that an unjustified claim is not necessarily untrue. Today, let’s continue with another example from science’s history to discuss what counts for evidence, when our beliefs are justified, and the extent to which we can lean on either as an epistemological security blanket. Let’s discuss cathode rays!
It’s en vogue to associate 1859 with Darwin, but I like to remember that year for physicist Julius Plücker, who noticed that a strange, green phosphorescence gathered around the negative electrode (cathode) of his tubed apparatus whenever he applied current to the positive electrode (anode). Based on his observations, Plücker reasoned that something was being emitted by the cathode, and a decade later his student—Johan Wilhelm Hittorf—demonstrated that objects placed between the cathode and an interior wall cast shadows. This led to the more specific conclusion that whatever was being emitted by the cathode traveled in straight lines.
Two mutually-exclusive hypotheses soon emerged and physicists found themselves divided. The first camp supported the hypothesis that cathode rays were atoms or gas molecules inside the tube that had become negatively charged. The second camp supported the hypothesis that cathode rays were not particles at all, but waves that moved through ether. In 1883, physicist Heinrich Hertz produced cathode rays inside an apparatus containing an electrometer, which did not register any charge. Of that experiment, Hertz said,
As far as the accuracy of the experiment allows, we can conclude with certainty that no electrostatic effect due to the cathode rays can be perceived.
Now, I appreciate the way Hertz worded that: it sounds like what we’d expect from any responsible scientist. Notice that unlike my high school biology teacher, he’s not taken facts and twisted them into agenda, dogma or premature conclusion. Rather, he simply stated nothing more and nothing less than what the results of the experiment allowed: as far as the accuracy of the experiment permits—IOW, proceeding on faith that the results were in fact accurate—scientists were able to justifiedly conclude the absence of an electrostatic effect.
The history of physics testifies to how wrong they were, regardless of whatever methodological certainty they felt justified their beliefs! There was an electrostatic effect being generated, even in Hertz’ experiment; it’s just that the electrometer Hertz used could not detect that effect. Regardless of however responsibly stated Hertz’ conclusion was, the body of requisite knowledge was insufficient, this time in the form of insufficient technology, which led to a false negative result.
Another decade or so passed, and British physicist J.J. Thomson repeated Hertz’ experiment in 1897. He initially obtained the same results. However, in that short decade, knowledge and technology had evolved such that Thomson could lower the air pressure inside the apparatus more than Hertz was able to do in 1883. Sure enough, Thomson detected what Hertz was literally unable to detect: the strange “cathode rays” showed clear lines of deviation towards the anode, which Thomson concluded as proof not only that they were charged particles, but negatively charged particles.
Today, it’s common knowledge that what Plücker and Hittorf and Hertz and Thomson referred to as “cathode rays” are not rays at all, but negatively charged subatomic particles more commonly referred to as electrons. Yet, during the time they were thought of as cathode rays, that belief—untrue as it was—was a justified belief, backed by repeatable experiments according to every principle of induction and falsification that scientists use today.
So, what’s the lesson to learn here, and what is the larger analogy in discussions of (a)theism?
There exists a certain subset of atheists and skeptics who lean with great confidence on the impression that each and every stepping stone of their philosophies constitute justified beliefs, but as the case of cathode rays demonstrates, beliefs deemed “justified” on account of repeatable experiments has nothing to do with whether those beliefs are in fact true. In fact, I’ll go out on an epistemological limb here, and provisionally argue that there is no objective, undeniable reason to prefer justified beliefs over unjustified ones: justified beliefs often prove false (as did belief in cathode rays), and unjustified beliefs often prove true (as did belief in asteroids). Court-of-law arguments would be a notable exception.
So, besides the obvious psychological self-soothing, what do we really gain to say that our beliefs are justified, if the quality of being justified is no reliable indicator of truth?