Join My New Course This January: Critical Thinking in the 21st Century

Starting January 1 (2015) I will be teaching an online course on Critical Thinking in the 21st Century: Essential Skills Everyone Should Master. Click that to register.

The required course text (which students should purchase as soon as possible) is Ken Manktelow, Thinking and Reasoning: An Introduction to the Psychology of Reason, Judgment and Decision Making (available in paperback … or on kindle for either purchase or rent: make sure you select the desired option before purchase). All other course materials (articles and video lectures) will be provided for free.

Official Course Description:

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Null Hypothesis My Ass (A Christmas Harangue)

Letter to the editor of Christian Apologetics Ministries (

You unbelievable wingnuts. You should totally fire your Professor of Apologetics, Jonathon Hold, from his position at your supposed Iowa University of Religion for being a baloneyhead. His article proposing The Null Hypothesis Project is full of vomitous flabergastery.

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Take My Course on Boghossian’s Making Atheists!

Photo of Peter Boghossian in casual professorial suit attire, gesturing and speaking on philosophy.

I will be co-teaching a class with Peter Boghossian on his book A Manual for Creating Atheists. It starts in a week (September 1), lasts a month, and uses his book as a course text. So if you want to take that class and use the print edition, buy it now! The kindle edition you can buy anytime. Details and registration here. Anyone interested in philosophy, or arguing one-on-one with believers, or creating more atheists or rational people in the world, will benefit from this course.

Indeed, the value of this course is threefold…

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On Evaluating Arguments from Consensus

I have often been asked how we should evaluate arguments from consensus. That’s where someone says “the consensus of experts is that P, therefore we should agree P is true.” On the one hand, this looks like an Argument from Authority, a recognized fallacy. On the other hand, we commonly think it should add weight to a conclusion that the relevant experts endorse it. Science itself is based on this assumption. As is religion, lest a religionist think they can defeat science by rejecting all appeals to authority–because such a tack would defeat all religion as well, even your own judgment, since if all appeals to authority are invalid, so is every appeal to yourself as an authority (on your religion, or even on your own life and experience).

And yet, it is often enough the case that a consensus of experts is wrong (as proved even by the fact that the scientific consensus has frequently changed, as has the consensus in any other domain of expertise, from history to motorboat repair). And our brains are cognitively biased to over-trust those we accept as authorities (the Asch effect), putting us at significant risk of false belief if we are not sufficiently critical of our relying on an expert. It’s only more complicated when we have warring experts and have to choose between them, even though we are not experts ourselves.

So what do we do?

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If You Learn Nothing Else about Bayes’ Theorem, Let It Be This

There are two things one learns from Bayes’ Theorem that are the windows to everything else Bayesian reasoning can ever teach you. And there is a lot it can teach you besides these two things. But here I’m cutting to the chase of the two that are most essential: theories cannot be argued in isolation, and prior assumptions matter.

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The Gettier Problem

Among my many forms of cobbled-together self-employment I provide specialized tutoring to graduate students in ancient history and philosophy around the world. Which is rewarding in lots of ways. One of which is when my student ends up correcting an error of mine. That’s when you know you are a successful teacher, and they are starting to surpass you in knowledge and acumen. I’ve actually been excited to report on this, and correct the record. Gratitude goes to Nick Clarke.

The short of it is that long ago in a comments thread on my blog many years ago I was incorrect in my analysis of Gettier Problems. I was on to the right solution, but I made the mistake of assuming an unsound conclusion could not be considered justified (and without realizing that’s what I was doing). Conclusions in Gettier Problems rely on false premises to reach true conclusions. I was right about that. But I wasn’t right about that being grounds to dismiss them.

Backstory is required. [Read more…]