This chapter has attempted to provide good reasons for a naturalistic, evidence-based pursuit of
knowledge that matters. Faith-based approaches to the meaning of life are limited because they
provide no grounds for choosing among the large array of religious faiths available. George W. Bush
and Osama bin Laden have their different faiths, but no basis of arguing that one is any better than the
other. Faith has been used to support many beliefs that we have good grounds to deem false, such as
placing the earth at the center of the universe. Faith has also been used to support many practices,
such as religious wars and torture, that from a broader perspective are more in tune with evil than
with good. Faith provides no way of resisting natural error tendencies in human thinking, including
confirmation bias and motivated inference.
In contrast, although evidence-based thinking is fallible, it has an effective method of correcting
errors, by systematically collecting new evidence, developing new explanatory hypotheses, and
selecting the best. Experimental methods such as those used in evidence-based medicine have the
advantage of making inference to the best explanation more effective by helping to identify cases
where observations are the result of bias, error, or chance. Inference to the best explanation enables
us to go beyond the limits of human sensory observations to accept theories about nonobservable
entities such as viruses and electrons. Done carefully, such inference does not suffice to justify belief
in God.
The philosopher Karl Popper is often cited as having shown that the crucial difference between
science and nonscience is falsifiability. Scientists are supposed to make bold conjectures and then
devise experiments that can refute them. Then the point of scientific evidence is not to show that
theories are true, as in inference to the best explanation, but rather to show that they are false.
According to Popper, what makes metaphysical theories bogus is that they are not falsifiable in this
way.
As a philosophy of science, however, Popper's view has many problems. No theory is strictly
falsifiable, because a theory can be used to make predictions only in conjunction with other
assumptions, such as experimental conditions and the reliability of instruments. Hence when a
prediction fails, a scientist cannot know whether to infer the falsity of the theory or that of one of the
assumptions. Historically, scientific theories are refuted only when a better theory comes along to
provide a better explanation of the experimental evidence. Popper's view of method expects scientists
to aim to show that their own theories are false, but such intentional self-refutation rarely happens.
The reason is not just that scientists grandiosely seek their own personal success; rather, the aims of
science include arriving at theories that accurately describe reality and provide informative
explanations of observed phenomena.
Therefore, the hallmark of science is not falsifiability but use of evidence in inferences to the best
explanation. Inference to the best explanation can lead us to conclude that many metaphysical theories
are not only falsifiable but false. For example, I argued earlier in this chapter that, based on available
evidence, we should conclude that there are no gods. Similarly, Chapter 3 argues that the hypothesis
of the existence of the soul can be judged to be false because of much greater evidence for the
alternative view that minds are brains.
Philosophical attempts to establish truths by a priori reasoning, thought experiments, or conceptual
analysis have been no more successful than faith-based thinking has been. All these methods serve
merely to reinforce existing prejudices. In contrast, evidence-based thinking often forces us to realize
that our old theories and the concepts embedded in them are inadequate, leading to the development
of new ones that fit much better with the full range of observations. That is why our search for
wisdom should not be based on faith or pure reason, but instead requires attention to all the relevant
evidence, especially what can be learned from research in psychology and neuroscience. A crucial
step in this search is the recognition that minds are brains.