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 1500 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 recently 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 recently 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 recently 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 recently 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.

If you would like to submit a comment about anything written here, please read our comments policy.


Follow me on

Copyright notice: © All rights reserved. Except for personal use or as permitted under the Australian Copyright Act, no part of this website may be reproduced, stored in a retrieval system, communicated or transmitted in any form or by any means without prior written permission. All inquiries should be made to the copyright owner, Tim Harding at, or as attributed on individual blog posts.

If you find the information on this blog useful, you might like to consider supporting us. Make a Donation Button


Filed under Uncategorized

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).


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

If you find the information on this blog useful, you might like to consider supporting us.

Make a Donation Button


Filed under Essays and talks


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.

Leave a comment

Filed under Uncategorized

50 Art Deco Works of Art You Should Know by Lynn Federle Orr (2015)

Books & Boots

This is a new addition to Prestel publishing’s successful ’50s’ series (cf 50 Women Artists You Should Know, which I read a month or so ago) and it does just what it says on the cover.

First there’s a ten-page introduction to Art Deco – then 50 double-page spreads showcasing works from nearly every artistic medium, from paintings and photography to furnishings and film, with the work of art on the right and a page of introduction/commentary/analysis on the left – all topped off by a page of recommended further reading.

Exactitude by Pierre Fix-Masseau (1932)Exactitude by Pierre Fix-Masseau (1932)

Some of these one page commentaries are really interesting. The one on the Bugatti poster starts with a fascinating overview of the phenomenal spread of cars, and the way they created an entire sub-culture of new roads, motels, gas stations, along with ads for all the necessary accessories, petrol, tyres, motoring gloves, goggles and…

View original post 958 more words

Leave a comment

Filed under Reblogs

Leisure fascism: Vegan says that a carnivore can’t eat tofu because it’s “cultural appropriation”

Banned for eating tofu? Because it is cultural appropriation? Is the world going mad?

Why Evolution Is True

Well, yes, this is from The Sun, but it does give names and I suspect it’s true (it’s reported at multiple places, including msn) .  Click on the screenshot for the LOLs:

The relevant bit of their exchange (in case you didn’t know, “tofurkey” is a turkey substitute made out of tofu, intended for consumption at Thanksgiving):

How well the termites have dined—or have not dined! I’m crying and shaking now. I can’t even. . .

Read the original article for more fun, including to see how the carnivorous tofu-eater was temporarily banned from her Facebook group.

h/t: Cindy

View original post

Leave a comment

Filed under Reblogs

Political evolution of USA senate 1789 – 2018

Leave a comment

Filed under Reblogs

Conversations with Dan: eudaimonia, Stoicism, and “the good life”

Footnotes to Plato

Monty Python Meaning of LifeWhat does it mean to live the good life? I’m positive Donald Trump, or Jeff Bezos, would give you very different answers from the one you’d get from me. But they are wrong and I’m right. After all, they are just rich and powerful people, I’m a philosopher…

Okay, kidding aside, “what is the meaning of life?” is the quintessential philosophical question, though one that these days is more likely to be satisfactorily answered by Monty Python than in the halls of a philosophy department (please make sure you get to the very end of the song). That is part of the reason why my friend Dan Kaufman and I do our occasional Sophia video series. The latest installment takes the question on directly by exploring the various meanings of the Ancient Greek word eudaimonia, often translated into English as happiness (which is not, really), or flourishing (close, but…

View original post 263 more words

Leave a comment

Filed under Reblogs

Life behind the Berlin Wall | The Economist

Leave a comment

Filed under Reblogs

E. O. Wilson: confused about free will

I have written an essay here arguing that we do have free will.


Why Evolution Is True

An article in the September 14 Harper’s, “On Free Will (and How the Brain is like a Colony of Ants”, gives an excerpt from Wilson’s book released that year, The Meaning of Human Existence.  In the piece and the passage below, Wilson appears to be a sort of compatibilist, but I find his discussion so confusing that I’m not quite sure what he’s trying to say. But his message is pretty clear: we can act as if we have a kind of free will, and those who deny it are doomed to insanity and a “deteriorating mind”.  The main bits:

The power to explain consciousness, however, will always be limited. Suppose neuroscientists somehow successfully learned all of the processes of one person’s brain in detail. Could they then explain the mind of that individual? No, not even close.

. . . Then there is the element of chance. The…

View original post 689 more words

Leave a comment

Filed under Reblogs

PinkerGate: The last word

Why Evolution Is True

Two days ago I wrote about how some social-media folks had distorted an eight-minute remark by Steve Pinker made at the Spiked event at Harvard: “Is political correctness why Trump won.” Pinker spoke about how certain facts had been censored or deemed taboo by the Left, and how the suppression of truth in that way simply drives people into the arms of the Right or the “alt-right” (whatever the “alt-right” is). If you listened to Pinker’s whole set of remarks, it was clear that he was against the alt-right and was calling for a degree of honesty by progressives that would not drive people rightward.

In my post, I showed how many people had willfully distorted Pinker’s remarks to make him seem a fan of the alt-right, something that anybody with a few neurons could have discerned had they listened to the whole eight-minute talk. But people kept excerpting just…

View original post 1,221 more words

Leave a comment

Filed under Reblogs

Surprise! Pinker smeared again by those who distort his words

Why Evolution Is True

There is no end of the kind of cherry-picking people will go to if they want to smear New Atheists. This post gives a prime example, with the target being Steve Pinker. (It’s always either Pinker, Sam Harris, or Richard Dawkins.)

On November 6, Spiked Magazine held one of its “Unsafe Space” events at Harvard, called “Is political correctness why Trump won?

Here’s the event description, the participants, and, below that, an 8-minute clip of Pinker giving his take on the issue.

The shock election of Donald Trump has sent many looking for answers. Why didn’t his outlandish statements, his ‘locker-room talk’ and his out-there views sink his candidacy in the way it would have sunk others? While many have chalked his win up to racism, xenophobia and misogyny – others suggest it was a revolt precisely against those who so casually throw around those labels. In short, the…

View original post 1,657 more words

Leave a comment

Filed under Reblogs

Karl Popper, Science, and Pseudoscience: Crash Course Philosophy #8

Some good points here about the differences between science and pseudoscience.

Utopia - you are standing in it!

View original post

1 Comment

Filed under Reblogs

Between holism and reductionism: a philosophical primer on emergence

Footnotes to Plato

A few years ago I was asked by the editor of the Biological Journal of the Linnaean Society to write a short paper introducing biologists to the philosophical literature on emergence, given recurrent, and sometimes confused, talk of “emergence” in biology. The result was “Between holism and reductionism,” published in 2014, the full version of which you can download here.

‘Emergence’ is a controversial concept with a convoluted history, in both science and philosophy. It is therefore not surprising that it has been misused and vilified, as well as more often than not misunderstood. Typically, the idea of emergence is brought up by researchers who are — for one reason or another — unhappy with an ultra-reductionist scientific program, preferring instead some kind of holism or interactionism in the way they approach their research questions (think of the always current debates on gene–environment interactions). Just as surely, biologists who…

View original post 2,080 more words

Leave a comment

Filed under Reblogs