honnêtement déraisonnable

You will mostly use this as a reaction. It usually follows C'est... (It is...). You can use it to describe a price, a person's behavior, or a set of rules. It functions as an adjective phrase. It doesn't change much based on gender because déraisonnable ends in an e. It sounds sophisticated but carries a sharp edge. It shows you have high standards for logic and fairness. Use it when you want to sound firm but controlled.

Use it when you see a €15 toast in a café. It is perfect for discussing rent prices in Paris. Use it when your boss asks you to work on a Sunday with no notice. It works well when a friend suggests hiking 30 kilometers in flip-flops. You can also use it in professional settings. It helps when a client makes a demand that is simply impossible. It signals that the conversation needs to get back to reality. It's a great tool for setting boundaries.

Don't use it for small, unimportant things. If you drop a pen, it’s not déraisonnable. Don't use it if you want to be extremely polite or submissive. It’s a bit too direct for a first meeting with a high-ranking official. Avoid using it to describe people you love during a sensitive moment. Calling your partner déraisonnable during a fight might make things much worse. It sounds a bit like you are judging their sanity. Save it for external situations or clear logical failures.

France is the land of René Descartes and the "Age of Enlightenment." Logic and reason are woven into the national identity. Being "reasonable" is a social virtue in France. If something is déraisonnable, it’s not just bad; it’s a violation of the social contract. The French love to debate the "juste prix" (fair price). This phrase is a staple of that cultural conversation. It reflects the French habit of being intellectually honest even when being negative.

You can swap honnêtement for other adverbs to change the flavor. Franchement déraisonnable is slightly more aggressive and common. Totalement déraisonnable means there is zero logic left. C'est un peu déraisonnable is a classic French understatement. It actually means it's very unreasonable, but you're being "polite." You might also hear C'est hors de toute raison, which is much more formal and dramatic.