"Sans logique" (English: "Without Logic") is a 1988 song recorded by French singer-songwriter Mylène Farmer. It was released on 20 February 1989 as the fourth and last single from her second studio album Ainsi soit je.... The song deals with schizophrenia, death, love and religion and was accompanied by a cinematic video which shows a human corrida. The single became a top ten hit in France.

After the successful songs "Sans contrefaçon" and "Pourvu qu'elles soient douces" and the huge sales of the parent album Ainsi soit je..., Farmer decided to release "Sans logique" as the fourth and last single from the album as she was preparing her first concert tour through France, Belgium and Switzerland. The B-side of the single, "Dernier Sourire", is a previously unavailable song about the death of a relative (though a live version of the cover "Je voudrais tant que tu comprennes", originally sung by Marie Laforêt, was first scheduled as the B-side).

"Sans logique" was actually recorded twice due to technical problems in the studio. The sentence "this is a blank formatted diskette" (sampled from an Ensoniq Mirage), which can be heard in the introduction of the song and later on, refers to this problem and was kept in the finished product. "Sans logique" was widely played on French radio during the year of its release was one of the top ten songs that yielded the most copyright royalties to the Société des auteurs, compositeurs et éditeurs de musique in 1989.

Shortly after the single's release, the European Workers Party used a photo from the video, where Farmer has white eyes and the horns on her head, with the subtitle "These artists who promote drugs and the ugliness". Farmer sued the secretary of the party, Jacques Cheminade, accusing him of having used her image without her consent and have made inappropriate and abusive remarks towards her. The Tribunal de grande instance de Paris found in Farmer's favour.

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