What did Apollinaris teach about Christ's human nature?

Apollinaris of Laodicea taught that in the Incarnation, Christ had a human body but did not possess a complete human mind or will. This belief was rooted in his view that, because Christ is divine, fully God, He could not also possess a fully human nature. Apollinaris proposed that the divine Logos took the place of a rational soul or mind in Jesus, which led him to assert that while Jesus had a body, He lacked a full human personhood that includes both a human will and a rational mind. This perspective was significant in early Christological debates because it was ultimately deemed a heresy by later councils, which reaffirmed the orthodox belief in the fullness of Christ's humanity, including both a human will and mind.

This understanding contrasted sharply with other views at the time, which held that Christ had a complete human nature, including both a rational soul and a human will. Apollinaris' doctrine was challenged and rejected in favor of positions that maintained the full humanity of Christ alongside His full divinity.