Geist und Seele wird verwirret (Spirit and soul become confused), BWV 35, is a church cantata by Johann Sebastian Bach. He composed the solo cantata for alto voice in Leipzig for the twelfth Sunday after Trinity and first performed it on 8 September 1726.

Bach composed the cantata in his fourth year as Thomaskantor (musical director) in Leipzig. The text is based on the day's prescribed reading from the Gospel of Mark, the healing of a deaf mute man. The librettist is Georg Christian Lehms, whose poetry Bach had used already in Weimar as the basis for solo cantatas. The text quotes ideas from the gospel and derives from these the analogy that as the tongue of the deaf mute man was opened, the believer should be open to admire God's miraculous deeds. The cantatas for this Sunday have a positive character, which Bach stressed in earlier works for the occasion by including trumpets in the score. In this work, he uses instead an obbligato solo organ in several movements.

The cantata is structured in seven movements in two parts, to be performed before and after the sermon. Both parts are opened by an instrumental sinfonia with solo organ, probably derived from concerto music composed earlier in Weimar or Köthen. The alto singer performs a sequence of alternating arias and recitatives, accompanied in all three arias by the organ as an equal partner. The Baroque instrumental ensemble is formed by two oboes, taille, strings and basso continuo. The alto part is demanding and was probably written with a specific singer in mind, as with the two other solo cantatas composed in the same period.