Coherence and Truth
Brains know reality through a combination of perception and inference to the best explanation of what
is observed. Such inference attempts to maximize explanatory coherence, which sometimes requires
rejection of what the senses tell us. Rejection of observations occurs both in everyday life, as when a
drunk decides that a double image of a person cannot be right, and in science, as when a researcher
throws out some experimental data that conflict with a well-supported theory. Hence gaining
knowledge is a matter of seeking coherence among many hypotheses and pieces of evidence, not of
starting with some indubitable foundation in sense experience or a priori knowledge and trying to
base everything else on that.
There are no foundations for knowledge, even though the overall reliability of perception justifies
recognizing that the results of observation should have a degree of priority in the maximization of
coherence. Knowledge is not a matter of pure coherence, because observational evidence does get
some priority and provides some constraint on utterly fanciful speculation. Nevertheless, I advocate a
kind of coherentism, the view that beliefs are justified by how well they fit with other beliefs and
with sensory experience. This coherentist view of knowledge meshes well with constructive realism
to provide an answer to the two questions that began this chapter: what is reality, and how do we
know it? Reality consists of objects and their properties that we can learn about through perception
and inference to the best explanation
nd inference to the best explanation.
In chapter 2, I described how inference to the best explanation in science differs from everyday
inference in employing mechanistic explanations and more thorough assessment of a broader range of
evidence gained from careful experiments. Hence well-supported scientific theories are usually a
more reliable guide to reality than is common sense, which is often derived from tradition rather than
systematic evaluation of alternative hypotheses with respect to evidence. So at any particular time,
we should accept what the best available scientific theories tell us, while acknowledging that the
collection of new evidence and the development of novel hypotheses may well lead to the eventual
conclusion that some current theories are not adequate representations of reality. Based on current
evidence, we should be content to recognize as real various forms of matter and energy, from atoms,
electrons, and quarks to human minds construed as brains.
Perception and inference to the best explanation are both fallible and require complex mental
processes, but there are nevertheless good reasons to resist idealism, the view that reality is
somehow dependent on mind. Evidence suggests that our universe is more than thirteen billions of
years old, but human minds have been around for only, at most, a few million. According to the fossil
record, the first mammals, whose brains were larger and more advanced than those of the reptiles
they evolved from, came along only around two hundred million years ago. Hence we have abundant
evidence that reality existed long before minds came along, and presumably will continue long after
all minds are extinct. Accordingly we must resist the Ptolemaic counterrevolutionary attempts to
reassuringly make human minds the center of reality. As chapter 7 will show, life can be meaningful
even if minds are brains rather than supernatural entities
Because we have good grounds for asserting the existence of mind-independent reality, we can
construe truth as correspondence between mental representations and aspects of reality. The relevant
representations include not only linguistic sentences, but also sensory images and extensions of them,
such as mental pictures we construct. The correspondence relation between representations and
reality need not simply be the binary true/false relation, but can involve approximations. A set of
representations such as a theory is approximately true if most of its claims are quantitatively close to
actual conditions in the world. Truth is then a legitimate aim of scientific and everyday theorizing,
along with explanation and prediction.