Learn to think critically in six weeks
One free university course on the data-flavored nonsense that fills your feed, one classic book that gives you a reusable checklist, and a daily habit of running real claims through it. Set the right expectation first: critical thinking is a practice, not a personality trait. Nobody is "just a skeptic." It's a set of moves you apply deliberately — especially to claims you want to be true. About 20 hours of study, then a habit you keep for life.
6 weeks · ~20 hours · the reflex to check a claim before you believe or share it
1.Calling Bullshit — Bergstrom & West (free course)
This is the University of Washington course on detecting and refuting the misuse of data, and the instructors put the entire thing online for free — syllabus, video lectures, readings, and case studies. It is precisely targeted at the modern problem: misleading charts, dodgy statistics, p-hacking, viral claims, and "the bullshit is in the numbers" sleight of hand. Watch the lecture videos in order and do the case studies, where you take apart a real published claim. This is the most useful free critical-thinking resource on the internet, and it's built for exactly the environment you live in.
Free
Calling Bullshit course →2.The Demon-Haunted World — Carl Sagan
Sagan's 1995 classic is where you get a portable toolkit you can carry into any argument. The chapter "The Fine Art of Baloney Detection" lays out nine tools for skeptical thinking — seek independent confirmation, encourage debate, run the numbers, apply Occam's razor, ask whether the claim is even falsifiable — and then catalogs twenty common logical and rhetorical fallacies. Memorize the kit. The rest of the book is the why: a warm, urgent case for science as a candle against the dark. Read the baloney chapter twice; the second time, test a real belief of your own against it.
~$18 paperback
The Demon-Haunted World →3.Run the kit on real claims, daily
A toolkit you never pick up does nothing. Every day, take one claim from your actual feed — a headline, a statistic in an ad, a confident post, a chart someone shared — and run it through the kit. Who is the source, and what do they gain if you believe it? Where's the original data? Does the number even mean what the headline says? Most importantly, practice on claims you want to be true, not just the ones from people you already distrust — that's where everyone's thinking quietly collapses. Ten minutes a day for six weeks turns the checklist into a reflex you run automatically.
Free (the work is the practice)
Worked case studies →If you want the formal logic underneath
This path is about spotting bad reasoning in the wild. If you'd rather build the rigorous foundation first — what actually makes an argument valid, how fallacies fail formally, how to construct an airtight case — start with logic instead, then come back here to apply it to messy real-world claims. The two are complements: logic is the grammar, critical thinking is using it under fire when the stakes and your own biases are real.
Why this path
Most "critical thinking" advice is a vague exhortation to be smarter, which helps no one. This path is concrete because the bottleneck is concrete: the problem isn't that you can't reason, it's that you don't reason on demand, and you reason least on the claims you most want to accept. Calling Bullshit drills the specific failure mode of our era — data-shaped nonsense — with worked examples. Sagan gives you a checklist small enough to actually remember. The daily reps build the only thing that matters: the habit of pausing before you believe. Skip the practice and you've just consumed two more pieces of content about thinking, which is the opposite of the goal.