What the cards are, and how they help

What the cards are

Each day you get one quote from a great thinker, a plain-English line saying what it means, and three quick questions. One asks you to apply the idea. The other two practise a reasoning skill, such as spotting a weak argument, a hidden assumption or a misleading number. It takes about two minutes.

How it helps, and what the evidence says

We don't promise to make you smarter, and no app honestly can. CritThinker gives you facts and tools. The research supports something narrower:

• Learning to name a reasoning trick and practising spotting it makes you better at catching it later. Studies of short bias-training games found lower bias weeks to months afterwards, including in a business decision people didn't know was a test.
• Practice works best with feedback, which is why every answer explains why it's right or wrong.
• Regular short refreshers help the skill last. One-off lessons tend to fade.
• Skills transfer best to situations that look like the practice, so the questions use everyday cases: adverts, headlines, advice, sales pitches and arguments with friends.

CritThinker trains the habit of pausing to ask: is this actually true, and how would I know?

The tactics we help you spot

Direct tactics in the argument itself:

• Attacking the person instead of the point: ad hominem, and 'you do it too' (tu quoque).
• Twisting what someone said: the straw man, and shifting the meaning of a word (equivocation).
• False choices: 'it's either this or disaster' (false dilemma), and 'one step leads to ruin' (slippery slope).
• Borrowed authority: 'experts say', 'everyone's doing it', 'it's natural', 'we've always done it'.
• Going in circles: the conclusion is hidden in the premise (circular reasoning).
• Moving the goalposts: changing the test once it's been passed, or putting the burden of proof on the wrong side.

Indirect tactics in framing, emotion and numbers:

• Emotional pressure: fear, flattery, urgency and guilt.
• Framing: '90% fat-free' versus '10% fat', and relative risk ('halves your risk') without the absolute numbers.
• Anchoring: a high first price makes the next one look like a bargain.
• Cherry-picked stories: one vivid anecdote or one success story, ignoring the failures (survivorship bias).
• False cause: it happened after, so it must have been caused by it.
• Loaded questions and distractions: 'Have you stopped wasting money?' and changing the subject (red herring).
• Our own biases: looking for what we already believe (confirmation bias), sticking with what we've already sunk money into (sunk cost), and judging by first impressions (the halo effect).

How the app gives you the tools

• A fallacies library of 27 fallacies and 15 biases, each with a definition, an example, what it's often confused with, and how to respond.
• 318 practice questions across nine skills, from spotting fallacies and biases to weighing evidence, telling fact from opinion, and reading numbers.
• A short daily habit with an explanation every time, the pattern the research supports.

Why learn from the great thinkers

• They show reasoning in action. Socrates questioned assumptions, Hume doubted easy cause and effect, Mill weighed the other side, and the Stoics separated facts from our reaction to them.
• Seeing serious minds disagree, such as Kant against Mill or Nietzsche against Plato, teaches you to weigh reasons, not reputations.
• Their ideas give you questions you can reuse: 'What would change my mind?' 'Is this in my control?' 'What's the strongest version of the other view?'
• We label every quote honestly as well attested, a paraphrase or misattributed, because even famous lines need checking.