Nineteenth-century doctors learned, slowly, that washing their hands saved lives. Nobody could see the germs, so the habit felt pointless until the death rates fell. Information works in a similar way. False claims, misleading images and half-truths are mostly invisible as they pass from screen to screen, and the damage shows up later, in bad decisions, broken trust and sometimes violence. Information hygiene is the name for daily habits that stop you catching and spreading bad information, the way handwashing stops you catching and spreading disease.

Truth is about the world, not the feed

The starting point is old and simple: a claim is true when it matches how things actually are. A post with a million shares is not more true than one with ten, and a claim that flatters your side is not more true than one that embarrasses it. Philosophers have built detailed theories of truth; here the idea serves as a practical rule. Popularity, repetition and emotional force are signals about people, not about the world. They tell you what is spreading among people, not what is so.

That rule sounds obvious, but modern feeds blur it. Ranking systems show what is popular and engaging, and the mind tends to treat what it sees often, from many directions, as settled. The habits in this course are ways of putting the question back where it belongs: what is the evidence that this matches reality?

Three kinds of information disorder

In 2017 the researchers Claire Wardle and Hossein Derakhshan wrote a report for the Council of Europe that gave the field a shared vocabulary. They called the whole problem information disorder and split it into three types, sorted by two questions: is it false, and is it meant to harm?

• Misinformation is false information shared without any intent to harm. An aunt forwarding a fake cure because she hopes it will help a relative is spreading misinformation.
• Disinformation is false information spread deliberately to deceive, for money, power or mischief. A made-up news site run for advertising income is a disinformation operation.
• Malinformation is true information used to cause harm, such as leaking someone's real home address to set a crowd on them.

The categories matter because they call for different responses. Misinformation is usually best met with patience and better sources. Disinformation calls for exposing who is behind it and why. Malinformation reminds us that hygiene is not only about accuracy: something can be true and still be wrong to spread. The same content can also change category as it travels. A disinformation campaign plants a false claim, and thousands of sincere people then pass it on as misinformation.

An old problem at a new speed

None of this is new in kind. In 1710 Jonathan Swift wrote in The Examiner: "Falsehood flies, and the Truth comes limping after it." What has changed is scale and speed. A rumor that once took weeks to cross a country can now cross the world in an afternoon, and anyone with a phone can produce text, images and video that look professional.

A duty to others

In 1877 the mathematician W. K. Clifford published an essay called "The Ethics of Belief." He told of a shipowner who stifled his doubts about an old, much-repaired ship, sent it to sea full of emigrants, and quietly collected the insurance when it sank. Clifford argued that the owner was guilty even had the ship survived, because he had no right to believe on the evidence he had: belief without enough evidence can be a moral wrong. His conclusion was blunt: "It is wrong always, everywhere, and for anyone, to believe anything upon insufficient evidence." Many philosophers think Clifford went too far, since people must act on incomplete evidence every day. But his core point fits an age of sharing well: belief is not purely private, because what we believe and pass on shapes what others believe and do.

This is where information hygiene connects to human dignity. Each person is owed the chance to reason about the real world. Deceiving people, even for a cause you think is good, treats them as tools to be steered rather than minds to be persuaded.

Worked example

A message arrives in a family group chat: a screenshot claiming that the local water supply has been poisoned, with advice to boil all water for a week. It is marked as forwarded many times. Apply the ideas from this level. First, notice the signals: forwarded often, urgent, frightening. Those describe how the message spread, not whether it is true. Second, ask the truth question: where would a real warning come from? A water utility or health department would post it on its own website and accounts, and a quick check finds nothing there. Third, sort the case. The cousin who forwarded it meant well, so in that cousin's hands it is misinformation, whatever its origin. The hygienic response is not mockery but a short reply linking the utility's actual page, and a suggestion to wait for official word before passing on alarms. The message took seconds to forward; the correction took two minutes. That gap is the subject of the next level.