Terms of Use

Reading and sharing

You are free to read, print and download pages from this site for personal study and for teaching. Reading an entry aloud to a class, or handing out copies of it, needs no permission.

Quoting several sentences with attribution and a link back needs no permission either.

Whole-entry republication

Republishing an entry verbatim, or feeding the corpus in bulk into another publishing site, a dataset or a training collection, requires written permission first. Write to [email protected] with the purpose and the scale.

Permission is normally granted for non-commercial teaching use; we just need to know where the material is going.

On accuracy

The formal definitions, identification signals and puzzle solutions are checked. For examples we prefer documented episodes and traceable statements, and we cite them; but historical accounts and published statistics are themselves disputed in the literature, so check the primary source before relying on one.

Every puzzle solution ships with its reasoning so that you can follow the steps yourself. If a step does not hold, tell us.

Not professional advice

This is teaching material about logic and reasoning. It is not legal, medical, financial, psychological or any other kind of professional advice. Consult a qualified professional before acting on a specific decision.

Claims, products, organisations or people appearing in examples are there to display the structure of an argument. Their appearance is not a recommendation and not a criticism.

External links and advertising

Pages may link to resources elsewhere; we are not responsible for their content or availability. Advertising on the site is served by Google AdSense; we do not control which ads appear, and an ad's presence is not an endorsement of the advertiser.

Data processing connected with advertising is described in the Privacy Policy.

Limitation of liability

The site is provided as is. We work to keep the content correct and the site reachable, but we are not liable for indirect losses arising from use of, or inability to use, this site.

If any clause here is found unenforceable, the remaining clauses continue to apply.

Changes to these terms

These terms may be revised as the site changes; the version published on this page is the one in force. Last updated 2026-09-18.