Critical Thinking - a Simple and Concise Look 5

 This post is one in a series on the book How to Think about Weird Things: Critical Thinking for a New Age by Theodore Shick, Jr. and Lewis Vaughn. (Fifth Edition)

Unless noted otherwise all quotes used in this series are from that book, usually with the page number noted in parenthesis.

The series should be read in order starting with the first post.

"If knowledge requires certainty, however, there is little that we know, for precious few propositions are absolutely indubitable." (Page 66)

"To demand that a proposition be certain in order to be known, then, would severely restrict the extent of our knowledge, perhaps to the vanishing point." (Page 66)

"So if knowledge doesn't require certainty, how much evidence does it require? It doesn't require enough to put the claim beyond any possibility of doubt but, rather, enough to put it beyond any reasonable doubt. There comes a point beyond which doubt, although possible, is no longer reasonable. It's possible, for example, that our minds are being controlled by aliens from outer space, but to reject the evidence of our senses on that basis would not be reasonable. The mere possibility of error is not a genuine reason to doubt. To have knowledge, then, we must have adequate evidence, and our evidence is adequate when it puts the proposition in question beyond a reasonable doubt.

A proposition is beyond a reasonable doubt when it provides the best explanation of something. In Chapter 6, we spell out the notion of best explanation in some detail. For now, it's important to realize that a claim doesn't have to possess any particular degree of probability in order to be beyond a reasonable doubt. All that is required is that it explain the evidence and account for it better than any of its competitors.

Even though we can't be absolutely sure that we're not living in the Matrix, we're justified in believing that we're not because the matrix hypothesis does not provide the best explanation of our sense experience. The hypothesis that our sensations are caused by a computer that directly stimulates our brains is not as simple as the hypothesis that they are caused by physical objects; it raises more questions than it answers; and it makes no testable predictions. The acceptability of a hypothesis is determined by how the amount of understanding it produces, and the amount of understanding produced by a hypothesis is determined by how well it systematizes and unifies our knowledge. Since the physical object hypothesis systematizes and unifies our knowledge better than the matrix hypothesis, we're justified in believing that we're not living in the Matrix.

We are justified in convicting someone of a crime if we have established his or her guilt beyond a reasonable doubt. Similarly, we are justified in believing  a proposition if we have established its truth beyond a reasonable doubt. But being justified in believing a proposition no more guarantees its truth than being justified in convicting someone guarantees his or her guilt. It is always possible that we have overlooked something that undermines our justification. Since we are not omniscient, we can never be sure that we have considered all the relevant evidence. Nevertheless, if we are justified in believing a proposition, we are claiming that it is true; indeed, we are justified in claiming that we know it. Such a claim could be mistaken, but it would not be improper, for our justification gives us the right to make such a claim. " (Page 66-67)

"If our belief in a proposition is not justified - if we have good reason to doubt it - then we have no right to claim that we know it. We have reasonable grounds for doubt when we have credible evidence to the contrary." (Page 68)

"In other words, if we have good reason for believing a proposition to be false, we are not justified in believing it to be true, even if all of our sensory evidence indicates that it is. When two propositions conflict with one another, we know that at least one of them must be false. Until we determine which one it is, we cannot claim to know either. Thus:

There is good reason to doubt a proposition if it conflicts with propositions we have good reason to believe.

The conflict of credible propositions provides reasonable grounds for doubt. And where there are reasonable grounds for doubt, there cannot be knowledge.

The search for knowledge, then, involves eliminating inconsistencies among our beliefs. When the conflict is between different reports of current observations, as in the case of the surface that appears to be pink, it's easy enough to find out which one is mistaken: Look more closely. When the conflict involves propositions that cannot be directly verified, finding the mistaken belief can be more difficult.

Sometimes we observe or are informed about things that seem to conflict with our background information - that vast system of well-supported beliefs we use to guide our thought and action, much of which falls under the heading "common sense." When this conflict happens, we have to decide whether the new piece of information is credible enough to make us give up some of our old beliefs. When we cannot directly verify a questionable claim, one way to assess its credibility is to determine how much is at stake in accepting it. When all other things are equal: 

The more background information a proposition conflicts with, the more reason there is to doubt it." (Page 68)

"The structure of our belief system can be compared to that of a tree. Just as certain branches support other branches, so certain beliefs support other beliefs. And just as bigger branches support more branches than little ones, so fundamental beliefs support more beliefs and ancillary ones. Accepting some dubious claims is equivalent to cutting off a twig, for it requires giving up only peripheral beliefs. Accepting others, however, is equivalent to cutting off a limb or even part of the trunk, for it requires giving up some of our most central beliefs." (Page 69)

"When there is good reason to doubt a proposition, we should proportion our belief to the evidence." (Page 70)

Here is a Bertrand Russell quote:

"(1) that when the experts are agreed, the opposite opinion cannot be held to be certain; (2) that when they are not agreed, no opinion can be regarded as certain by a non-expert; and (3) when they all hold that no sufficient grounds for a positive opinion exist, the ordinary man would do well to suspend his judgement." Bertrand Russell (Page 72)

"These propositions may seem mild, yet, if accepted, they would absolutely revolutionize human life.

The opinions for which people are willing to fight and persecute all belong to one of these three classes which this skepticism condemns. When there are rational grounds for an opinion, people are content to set them forth and wait for them to operate. In such cases, people do not hold their opinions with passion; they hold them calmly, and set forth their reasons quietly. The opinions that are held with passion are always those for which no good ground exists; indeed the passion is the measure of the holder's lack of rational conviction." Bertrand Russell (Page 72)

"There is good reason to doubt  a proposition if it conflicts with expert opinion." (Page 72)

"Just because someone is an expert in one field doesn't mean that he or she is an expert in another." (Page 73)

I want to contrast this with a quote from Carl Sagan:

“Arguments from authority carry little weight – authorities have made mistakes in the past. They will do so again in the future. Perhaps a better way to say it is that in science there are no authorities; at most, there are experts.”

― Carl Sagan, The Demon-Haunted World: Science as a Candle in the Dark

Sagan pointed out the crucial fact that accepting something as true merely because an authority said it is a road to accepting all kinds of things with no real basis. Sometimes authorities are right, sometimes they are wrong. Sometimes they agree on an issue (and could be right or wrong) and sometimes they disagree. You can have two authorities who have equal credentials, experience and education to your knowledge and they can profoundly disagree.

You have to be able to weigh evidence, consider arguments and use your own judgement ultimately. Sometimes we simply lack the education to form an educated opinion about a topic and we need to decide which expert to listen to. Two doctors can disagree about treatment and we have to either have a treatment or not. We don't have time to become a doctor before deciding. We sometimes have to pick which experts to follow the advice of. If we do this we should understand what we actually know and what we are relying on someone else to understand. These are important distinctions.

As no authority or expert Margaret is infallible, no idea from an authority or expert should ever be accepted merely based on the source. Similarly as non-expert opinions are sometimes correct no idea should be rejected merely based on the source.

We may need to choose to trust people and we are best off being very careful in this regard. We don't want to mistake an evaluation of expertise or general trustworthy character with knowledge and evidence.

If you don't have solid evidence to support a claim then it's not consistently reliable to be too trusting of experts or people who we feel are trustworthy. We eventually get burned if we keep playing with this fire. 

If at all possible we should find evidence to support the claims of people and understand that grounds for reasonable doubt do not disappear just because we wish it so. 

COHERENCE AND JUSTIFICATION

Ordinarily, if a proposition fails to cohere with the rest of our beliefs, we are not justified in believing it. So coherence is a necessary condition for justification. But is it also sufficient? If a proposition coheres with the rest of our beliefs, are we justified in believing it? Remarkably enough, the answer to this question is no. Just because a proposition coheres with our beliefs, it is not necessarily likely to be true. " (Page 75)

"The traditional sources of knowledge - perception, introspection, memory, and reason - are not infallible guides to the truth, for our interpretations of them can be negatively affected by all sorts of conditions, many beyond our control. But if we have no reason to believe that such conditions are present, then we have no reason to doubt what these sources of knowledge tell us. The principle that emerges from these considerations is this:

If we have no reason to doubt what's disclosed to us through perception, introspection, memory, or reason, then we're justified in believing it.

In other words, the traditional sources of knowledge are innocent until proven guilty. Only if we have good reason for believing that they are not functioning properly should we doubt them." (Page78)

Whole books and subjects are devoted to exploring the weaknesses and vulnerabilities in our perception, introspection, memory and reason.

I have read and written on quite a few of them such as Subliminal by Leonard Mlodinow and A Theory of Cognitive Dissonance by Leon Festinger and Thinking, Fast and Slow by Daniel Kahneman. Suffice to say the subject is well worth exploring but the authors are correct - unless we know good reasons to NOT TRUST our perception, introspection, memory and reason we should rely on them. After all, it would very hard to know or believe anything if we didn't rely on and trust these essential tools.  

"SUMMARY

Factual knowledge concerns the truth of propositions and is therefore referred to as propositional knowledge. We possess this kind of knowledge when we have a true belief supported by good reasons. Reasons confer probability on propositions. The better the reasons, the more likely it is that the proposition they support is true. Some think that to know a proposition, we must have reasons that establish it beyond a shadow of a doubt. But knowledge requires only that we have reasons good enough to put the proposition beyond s reasonable doubt. A proposition is beyond a reasonable doubt when it provides the best explanation of something.

If we have good reasons to doubt a proposition, then we cannot be said to know it. We have good reasons to doubt it if it conflicts with other propositions we have good reason to believe. We also have good reason to doubt it if it conflicts with other propositions we have good reason to believe. We also have good reasons to doubt it if it conflicts with our background information - our massive system of well-supported beliefs, many of which we regard as common sense. The more background information a proposition conflicts with, the more reason there is to doubt it. Likewise, since the opinions of experts are generally reliable, we have good reason to doubt a proposition if it conflicts with such opinions. But we must be careful: Just because someone is an expert in one field doesn't mean that he or she is an expert in another.

The traditional sources of knowledge are perception, introspection, memory, and reason. They are not infallible guides to the truth, for our use of them can be distorted by many factors. But if we have no reason to doubt what's disclosed to us through these, then we're justified in believing it. Faith - unjustified belief - is often considered to be another source of knowledge. But unjustified belief cannot constitute knowledge. Intuition conceived as a kind of sixth sense like ESP cannot be regarded as a source of knowledge without evidence showing that it is in fact a reliable guide to truth. Intuition as a type of heightened sensory perception, however, has been shown to be actual. Some people consider mystical experiences reliable guides to deep truths. They may be correct, but we cannot simply assume that they are - we must corroborate the experiences by applying our usual tests of knowledge.

In light of this, we can ask whether we have good reasons for believing in astrology. The answer is no: The claim that astrology is true is not supported by any good evidence, and it conflicts with a tremendous amount of our background information. " (Page 95-96)