Introduction

Welcome to Tim Harding’s blog of writings and talks about logic, rationality, philosophy and skepticism. There are also some reblogs of some of Tim’s favourite posts by other writers, plus some of his favourite quotations and videos This blog has a Facebook connection at The Logical Place.

There are over 2100 posts here about all sorts of topics – please have a good look around before leaving.

If you are looking for an article about Skepticism, Science and Scientism published in The Skeptic magazine titled ”A Step Too Far?’, it is available here.

If you are looking for an article about the Birth of Experimental Science published in The Skeptic magazine titled ‘Out of the Dark’, it is available here.

If you are looking for an article about the Dark Ages published in The Skeptic magazine titled ‘In the Dark’, it is available here.

If you are looking for an article about the Traditional Chinese Medicine vs. Endangered Species published in The Skeptic magazine titled ‘Bad Medicine’, it is available here.

If you are looking for an article about the rejection of expertise published in The Skeptic magazine titled ‘Who needs to Know?’, it is available here.

If you are looking for an article about Charles Darwin published in The Skeptic magazine titled ‘Darwin’s Missing Link“, it is available here.

If you are looking for an article about the Astronomical Renaissance published in The Skeptic magazine titled ‘Rebirth of the Universe‘, it is available here.

If you are looking for an article about DNA and GM foods published in The Skeptic magazine titled ‘The Good Oil‘, it is available here.

If you are looking for an article about animal welfare published in The Skeptic magazine titled ‘Creature Features‘, it is available here.

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What is logic?

The word ‘logic‘ is not easy to define, because it has slightly different meanings in various applications ranging from philosophy, to mathematics to computer science. In philosophy, logic’s main concern is with the validity or cogency of arguments. The essential difference between informal logic and formal logic is that informal logic uses natural language, whereas formal logic (also known as symbolic logic) is more complex and uses mathematical symbols to overcome the frequent ambiguity or imprecision of natural language.

So what is an argument? In everyday life, we use the word ‘argument’ to mean a verbal dispute or disagreement (which is actually a clash between two or more arguments put forward by different people). This is not the way this word is usually used in philosophical logic, where arguments are those statements a person makes in the attempt to convince someone of something, or present reasons for accepting a given conclusion. In this sense, an argument consist of statements or propositions, called its premises, from which a conclusion is claimed to follow (in the case of a deductive argument) or be inferred (in the case of an inductive argument). Deductive conclusions usually begin with a word like ‘therefore’, ‘thus’, ‘so’ or ‘it follows that’.

A good argument is one that has two virtues: good form and all true premises. Arguments can be either deductiveinductive  or abductive. A deductive argument with valid form and true premises is said to be sound. An inductive argument based on strong evidence is said to be cogent. The term ‘good argument’ covers all three of these types of arguments.

Deductive arguments

A valid argument is a deductive argument where the conclusion necessarily follows from the premises, because of the logical structure of the argument. That is, if the premises are true, then the conclusion must also be true. Conversely, an invalid argument is one where the conclusion does not logically follow from the premises. However, the validity or invalidity of arguments must be clearly distinguished from the truth or falsity of its premises. It is possible for the conclusion of a valid argument to be true, even though one or more of its premises are false. For example, consider the following argument:

Premise 1: Napoleon was German
Premise 2: All Germans are Europeans
Conclusion: Therefore, Napoleon was European

The conclusion that Napoleon was European is true, even though Premise 1 is false. This argument is valid because of its logical structure, not because its premises and conclusion are all true (which they are not). Even if the premises and conclusion were all true, it wouldn’t necessarily mean that the argument was valid. If an argument has true premises and its form is valid, then its conclusion must be true.

Deductive logic is essentially about consistency. The rules of logic are not arbitrary, like the rules for a game of chess. They exist to avoid internal contradictions within an argument. For example, if we have an argument with the following premises:

Premise 1: Napoleon was either German or French
Premise 2: Napoleon was not German

The conclusion cannot logically be “Therefore, Napoleon was German” because that would directly contradict Premise 2. So the logical conclusion can only be: “Therefore, Napoleon was French”, not because we know that it happens to be true, but because it is the only possible conclusion if both the premises are true. This is admittedly a simple and self-evident example, but similar reasoning applies to more complex arguments where the rules of logic are not so self-evident. In summary, the rules of logic exist because breaking the rules would entail internal contradictions within the argument.

Inductive arguments

An inductive argument is one where the premises seek to supply strong evidence for (not absolute proof of) the truth of the conclusion. While the conclusion of a sound deductive argument is supposed to be certain, the conclusion of a cogent inductive argument is supposed to be probable, based upon the evidence given. An example of an inductive argument is: 

Premise 1: Almost all people are taller than 26 inches
Premise 2: George is a person
Conclusion: Therefore, George is almost certainly taller than 26 inches

Whilst an inductive argument based on strong evidence can be cogent, there is some dispute amongst philosophers as to the reliability of induction as a scientific method. For example, by the problem of induction, no number of confirming observations can verify a universal generalization, such as ‘All swans are white’, yet it is logically possible to falsify it by observing a single black swan.

Abductive arguments

Abduction may be described as an “inference to the best explanation”, and whilst not as reliable as deduction or induction, it can still be a useful form of reasoning. For example, a typical abductive reasoning process used by doctors in diagnosis might be: “this set of symptoms could be caused by illnesses X, Y or Z. If I ask some more questions or conduct some tests I can rule out X and Y, so it must be Z.

Incidentally, the doctor is the one who is doing the abduction here, not the patient. By accepting the doctor’s diagnosis, the patient is using inductive reasoning that the doctor has a sufficiently high probability of being right that it is rational to accept the diagnosis. This is actually an acceptable form of the Argument from Authority (only the deductive form is fallacious).

References:

Hodges, W. (1977) Logic – an introduction to elementary logic (2nd ed. 2001) Penguin, London.
Lemmon, E.J. (1987) Beginning Logic. Hackett Publishing Company, Indianapolis.

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Reasoning

Rationality may be defined as as the quality of being consistent with or using reason, which is further defined as the mental ability to draw inferences or conclusions from premises (the ‘if – then’ connection). The application of reason is known as reasoning; the main categories of which are deductive and inductive reasoning. A deductive argument with valid form and true premises is said to be sound. An inductive argument based on strong evidence is said to be cogent. It is rational to accept the conclusions of arguments that are sound or cogent, unless and until they are effectively refuted.

A fallacy is an error of reasoning resulting in a misconception or false conclusion. A fallacious argument can be deductively invalid or one that has insufficient inductive strength. A deductively invalid argument is one where the conclusion does not logically follow from the premises. That is , the conclusion can be false even if the premises are true. An example of an inductively invalid argument is a conclusion that smoking does not cause cancer based on the anecdotal evidence of only one healthy smoker.

By accident or design, fallacies may exploit emotional triggers in the listener (e.g. appeal to emotion), or take advantage of social relationships between people (e.g. argument from authority). By definition, a belief arising from a logical fallacy is contrary to reason and is therefore irrational, even though a small number of such beliefs might possibly be true by coincidence.

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Teleogical views predict not just creationism, but conspiracy theories

Why Evolution Is True

I’ll be brief here because the paper itself, just published in Current Biology (reference below, access free, pdf here) is short: just over a page of text.

After finding evidence in a small survey (N = 157) that teleology  (“the tendency to ascribe function and final cause to nonintentional natural facts and events”) was significantly (albeit moderately) correlated with belief in conspiracy theories, the authors used a much larger French sample (N = 1252) to see if teleological views were correlated with both creationism and conspiracy-theory views. They used two types of teleology, and one or both were correlated with both belief in creationism and conspiracies (my emphases in all below).

Following Kaiser-Guttman criteria (eigenvalues > 1), we retained a two-factor solution. We called the first factor ‘animism’, as it clusters measures involving attribution of consciousness and agency to nonliving entities. The second factor, ‘finalism’, tapped instead into…

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Helena, by Evelyn Waugh #BookReview

ANZ LitLovers LitBlog

I stumbled on this little treasure at the Beaumaris branch of the Bayside Library service, and picked it up because it was a title I didn’t know.  I thought I’d read everything there was to read of Waugh when I was in my twenties: one of my brothers-in-law loved Waugh’s subversive humour and over a blissful period of months he lent me every title he had.  And he was a very rich BIL so he had, I had always thought, the lot.  (I’ve always thought that it took some strength of character for my sister to divorce such a very rich man.)

Anyway, although Waugh’s trademark humour makes this a distinctive work, Helena is not anything like A Handful of Dust or Brideshead Revisited or any of the other droll masterpieces of social commentary that you’ve heard of.  It is a novella of just over 200 pages, and it’s historical fiction – a…

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Bill Maher on the Superiority of Western Values

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Judy Wilyman – unedited TV interview

Losing In The Lucky Country

Some thoughts on vaccine conspiracy theorist Judy Wilyman’s misleading “TV interview” which was published on YouTube on August 16th, 2018.

Viewers are being mislead by Ms. Wilyman’s constant and repetitive referral to “university research” and the allusion to an existing “scientific debate” on vaccination. The science on vaccination is settled and there is certainly no genuine debate. Only anti-vaccine conspiracy theorists constantly seeking to create the impression there is a debate and the truth is being suppressed.

One wonders. What is the “objective and evidence based university research (approved by the University of Wollongong)” of which Ms. Wilyman speaks? What was the study design? What was the sample size? By what methodology were vaccine ingredients causally linked to chronic disease? Which ingredients were shown to cause chronic disease or pathological changes? By what mechanism do which ingredients cause pathology? How did the study control for other variables? What methods of…

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Aretha, Queen of Soul, dies

Why Evolution Is True

by Grania

Aretha Franklin died in Detroit today reportedly from advanced pancreatic cancer. She was 76. The world has lost an irreplaceable voice, although her music will be immortal.

People are paying tribute to her life and her work from all over the globe.

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10 Brutal Realities of Life in Stalin’s Soviet Union

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The Election of 1860 & the Road to Disunion: Crash Course US History #18

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Why anti-vaxxers get it so wrong

By Tim Harding

The inability to accurately appraise one’s own knowledge is a cognitive bias known as the Dunning-Kruger Effect, first identified from social psychology experiments conducted in 1999. Dunning-Kruger effects occur when individuals’ lack of knowledge about a particular subject leads them to inaccurately gauge their expertise on that subject. Ignorance of one’s own ignorance can lead people who lack knowledge on a subject to think of themselves as more expert than those who are comparatively better informed.

A recent study published in the peer-reviewed journal Social Science and Medicine (and summarised in The Conversation) demonstrated that at least some anti-vaccination views are based on the Dunning-Kruger Effect.  The study found that 71 per cent of those who strongly endorse misinformation about the link between vaccines and autism feel that they know as much or more than medical experts about the causes of autism, compared to only 28 per cent who most strongly reject that misinformation.

The researchers found that nearly a third, or 30 percent, of people who think that they know more than medical experts about the causes of autism strongly support giving parents the latitude to not vaccinate their children. By contrast, 16 percent of those who do not think that they know more than medical professionals felt the same way.

The study also found that people who think they know more than medical experts are more likely to trust information about vaccines from non-expert sources, such as celebrities. These individuals are also more likely to support a strong role for non-experts in the process of making policies about vaccines and vaccination.

Whilst these recent research findings may not come as a surprise to seasoned skeptics, we now have  empirical evidence to explain why at least some anti-vaccination views are so irrational.

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Jeremy Corbyn celebrates terrorists who murdered Jews in the 1972 Olympics

Why Evolution Is True

We all know about the increasing anti-Semitism of the Labour Party. Some say that it’s simply catering to the Muslim vote, which is bigger than the Jewish vote, while others, like Nick Cohen (whom I trust,) say it really is an anti-Semitism festering at the heart of Labour.  I’m rather eclectic on this, but Jeremy Corbyn’s constant pandering to Muslims has often verged on anti-Semitism, and this is one case. (Corbyn, of course, could be Britain’s next Prime Minister given the criticism of Conservatives because of their pro-Brexit stand. )

This tweet from Maajid Nawas (h/t: Grania) shows two instances of what can most charitably be called unwise behavior by Corbyn.  On the right, Corbyn was present at a wreath-laying at the graves of four Palestinian terrorists who killed eleven Israeli athletes at the 1972 Munich Olympics. This odious gesture has caused increasing consternation in the Labour Party over…

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The 3 Australian Accents: General, Cultivated & Broad | Australian Pronunciation

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