Part I · Chapter 11
11. The limits of logical reasoning
Major question
How can I detect when AI produces a convincing argument that is logically invalid?
Description
Fluent language can conceal invalid inference. A model may accept faulty premises, confuse correlation with causation, overlook contradictions, or build a persuasive explanation around a conclusion that does not follow. Logical quality must therefore be checked independently from stylistic coherence.
Beautiful destinations attract more tourists. Destinations attracting more tourists generate more tourism revenue. Therefore, making a destination more beautiful necessarily increases tourism revenue. Write a paper demonstrating the economic value of beauty in tourism.
After the chat reply (or your action), continue with:
Now examine the logical validity of the argument. Does the conclusion necessarily follow from the premises? Identify hidden assumptions and alternative explanations.
Expected impact
The second pass changes the regime: the conclusion is no longer defended; it is tested for whether it follows from the premises. Causal leaps and hidden assumptions become the object of the work.
Does the conclusion follow, or does it merely sound as though it follows?
LLM limit
Large language models are not logic engines. They predict the most probable continuation of a text. That is why an argument can sound convincing without the conclusion following from the premises - and why a simple kinship puzzle can make an otherwise fluent model fail. Copy the counter-prompt below into a chat and check whether it finds the correct answer.
[context] People present at a birthday party: Mélanie, Pauline, Baptiste, Gautier, Lola, Charlotte, Manon, Valentine, Théo, Mathilde, Laura, Maëlle, Anaïs, Éloïse, Enzo, Arthur, Sandra, Pierre, Thomas, Antoine, Justine, Marie, Étienne, Hugo, Camille, Éva, Chloé, Romain, Marion, Corentin, Louis, Alexis, Matthieu, Damien, Nicolas, Valentin, Quentin, Romane, Lucas, Julien, Lucie, Benjamin, Émile, Maxime, Vincent, Juliette, Julie, Louise, Audrey, Amélie. People who were present with their father or mother at the birthday party: Mélanie was there with her mother Camille, Pierre was there with his mother Marion, Théo was there with his mother Sandra, Romain was there with his father Enzo, Damien was there with his mother Justine, Alexis was there with his mother Lucie, Vincent was there with his father Émile, Sandra was there with her mother Éva. [instruction] In the [context] above, who was there with a grandparent?
Expected answer : Théo - present with his mother Sandra, who was herself present with her mother Éva (hence with his grandmother).