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 2,300 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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Media, relieved that Notre Dame relics were saved, acts as if they were real

Why Evolution Is True

The fire at Notre Dame is out, and much of the main building was spared, though it will take years, if ever, to bring it back to where it was before. I’m not sure about the status of its famous stained-glass windows, though one photo seems to show that a big one is gone, for, after all, the glass was held together with easily-melted lead. The cause of the disaster has not been determined, and may never be.

All in all, it’s not the disaster I feared; here’s what it looks like today:

Photo from the NY Times. Thibault Camus/Associated Press

President Macron has pledged that it will be rebuilt, and private donors have already given millions to that purpose, with the LVMH Group having donated 200 million Euros.

While I was watching the news last night, they had a special report from a correspondent who was talking about…

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Seven Clues to the Origin of Life by A.G. Cairns-Smith (1985)

Books & Boots

The topic of the origin of life on the Earth is a branch of mineralogy. (p.99)

How did life begin? To be more precise, how did the inorganic chemicals formed in the early years of planet earth, on the molten rocks or in the salty sea or in the methane atmosphere, transform into ‘life’ – complex organisms which extract food from the environment and replicate, and from which all life forms today are ultimately descended? What, when and how was that first momentous step taken?

Thousands of biologists have devoted their careers to trying to answer this question, with the result that there are lots of speculative theories.

Alexander Graham Cairns-Smith (1931-2016) was an organic chemist and molecular biologist at the University of Glasgow, and this 120-page book was his attempt to answer the Big Question.

In a nutshell he suggested that life derived from self-replicating clay crystals. To use…

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Readers’ wildlife photos

Why Evolution Is True

We’re going to count astronomy as wildlife today, as it’s Honorary Wildlife®. These two swell Cosmos Photos come from reader Tim Anderson in Australia, and I’ve indented his notes. As always, click on the photos to enlarge them.

It is the galaxy season in the Southern Hemisphere, which is to say that there are large number of galaxies up in the night sky down in these parts.
Here is one of them. This is an image of the Sombrero Galaxy (catalogued as M104 in the Messier catalogue). The dark dust lane that crosses the galaxy horizon is where new stars are forming.The galaxy is approximately 28 million light-years away from us. The image was formed from sixty 30-second frames taken using a colour camera and a 127mm refracting telescope.
Attached is an image of NGC 2997, a large barred spiral galaxy in the local supercluster. It is approximately 25…

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The Double Helix by James Watson (1968)

Books & Boots

The short paper by James Watson and Francis Crick establishing the helical structure of the DNA molecule was published in the science journal, Nature, on April 25, 1953. The blurb of this book describes it as the scientific breakthrough of the 20th century. Quite probably, although it was a busy century – the discovery of antibiotics was quite important, too, not to mention the atom bomb.

James Watson and Francis Crick with their DNA model at the Cavendish Laboratories in 1953

Anyway, what makes this first-person account of the events leading up to the discovery such fun is Watson’s prose style and mentality. He is fearless. He takes no prisoners. He is brutally honest about his own shortcomings and everyone else’s and, in doing so, sheds extraordinarily candid light on how science is actually done. He tells us that foreign conferences where nobody speaks English are often pointless. Many scientists…

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The Periodic Kingdom: A Journey Into the Land of the Chemical Elements by Peter Atkins (1995)

Books & Boots

Chemistry is the science of changes in matter. (p.37)

At just under 150 pages long, A Journey Into the Land of the Chemical Elements is intended as a novel and imaginative introduction to the 118 or so chemical elements which are the basic components of chemistry, and which, for the past 100 years or so, have been laid out in the grid arrangement known as the periodic table.

The periodic table explained

Just to refresh your memory, it’s called the periodic table because it is arranged into rows called ‘periods’. These are numbered 1 to 7 down the left-hand side.

What is a period? The ‘period number’ of an element signifies ‘the highest energy level an electron in that element occupies (in the unexcited state)’. To put it another way, the ‘period number’ of an element is its number of atomic orbitals. An orbital is the number of orbital positions…

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The Spice Islands Voyage, in Search of Wallace, by Tim Severin

ANZ LitLovers LitBlog

The Spice Islands Voyage, in Search of Wallace is the June choice for our Indonesian bookgroup but I’m reading it early because it’s hard to source and we need to circulate the library copy as best we can.

It’s more than a travel book.  Tim Severin is an explorer who specialises in recreating historic voyages, and the list of his books at Wikipedia is impressive:

  • Tracking Marco Polo (1964) – Motorcycle ride from Venice to Central Asia along the Silk Road
  • Explorers of the Mississippi (1968)
  • The Golden Antilles (1970)
  • The African Adventure (1973)
  • Vanishing Primitive Man (1973)
  • The Oriental Adventure: Explorers of the East (1976)
  • The Brendan Voyage (1978) – Sailing a leather currach from Ireland to Newfoundland
  • The Sindbad Voyage (1983) – Sailing an Arab dhow from Muscat, Oman to China
  • The Jason Voyage: The Quest for the Golden Fleece (1986) – Sailing from Greece to Georgia
  • The…

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Livestream of black-hole announcement at 9 a.m. EDT (1300 GMT)

Amazing!

Why Evolution Is True

As I mentioned yesterday, today is the day that the Event Horizon Telescope team will announce “a major discovery”, which will almost certainly include the first photographic image of a black hole.

The announcement will be livestreamed at 9 a.m. Eastern Time in the US or 1300 GMT. Sadly, I’ll be on my way to the dentist’s for my semiannual tooth cleaning, and will have to miss this, but you don’t have to. Just go to the YouTube site below just before the times noted above, and you’ll see this exciting announcement.

I’ll watch it afterwards, but it won’t have the emotional impact of the live announcement. So it goes.

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In which I visit Woke Left websites

I liked the movie ‘The Green Book’ too.

Why Evolution Is True

It’s really time I stopped looking at HuffPost, as my friends tell me repeatedly. But I still like to look at Woke Left websites, just like I look at conservative and centrist or center-Left websites: just to see what’s going on.

I’ve managed to break the habit of looking at Salon, though, spending a bit of time there today, I was appalled to see how mindlessly authoritarian it has become: it’s almost a caricature of Authoritarian rhetoric. One example: I saw the movie Green Bookon the plane to Europe, and thought it was pretty damn good, though I was of course aware that the family of the black protagonist Don Shirley objected to its factual inaccuracies. But it was a movieand not a biography. Liberties were and are taken in movies like this.

Salon‘s objection, though, was the familiar one that Green Book was a “white…

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The Last Three Minutes by Paul Davies (1994)

Books & Boots

The telescope is also a timescope. (p.127)

Davies (b.1946) is an English physicist, writer and broadcaster. He’s written some 25 books, and hosted radio and TV series popularising science, especially in the areas of cosmology and particle physics, with a particular interest in the links between modern scientific theory and religion – hence his books God and the New Physics and The Mind of God.

The Last Three Minutes was his sixteenth book and part of the Science Masters series, short, clear primers written by experts across all areas of science. The advantage of The Last Three Minutes is that it is a clear explication of all the theories in this area; the drawback is that it is now precisely 25 years out of date, a long time in a fast-moving field like cosmology.

On the plus side, although the book might not capture the very latest discoveries and thinking, many…

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The Origin of the Universe by John D. Barrow (1994)

Books & Boots

In the beginning, the universe was an inferno of radiation, too hot for any atoms to survive. In the first few minutes, it cooled enough for the nuclei of the lighter elements to form. Only millions of years later wold the cosmos be cool enough for whole atoms to appear, followed soon by simple molecules, and after billions of years by the complex sequence of events that saw the condensation of material into stars and galaxies. Then, with the appearance of stable planetary environments, the complicated products of biochemistry were nurtured, by processes we still do not understand. (The Origin of the Universe, p.xi)

In the late 1980s and into the 1990s science writing became fashionable and popular. A new generation of science writers poured forth a wave of books popularising all aspects of science. The ones I remember fell into two broad categories, evolution and astrophysics. Authors such as…

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