German advocate for and teacher of oralism (one of many early communication methods devised for use by hearing-impaired individuals) in the education of the deaf.

After receiving only a village school education, Heinicke enlisted in the army, where he found time to indulge his intense fondness for books and his interest in languages. He studied Latin and French and began to teach both languages. He was stirred by the publication of Surdus loquens (1692; “The Talking Deaf”) by a Swiss physician who had succeeded in teaching deaf persons to speak. This impression remained with him when he was taken prisoner by the Prussians during the Seven Years' War. He managed to escape and eventually became secretary to the Danish ambassador in Hamburg. In 1769 the ambassador helped Heinicke secure a teaching position in nearby Eppendorf, where he found his real calling in the instruction of deaf children.

In 1778 Heinicke opened the first German public school for the education of the deaf. He insisted that lipreading was the best training method because it made his students speak and understand the language as it was used in society. He bitterly opposed dependence on sign language and in 1780 published a book attacking the Abbé de l'Epée, whose Parisian school for the deaf taught communication through gestures.

In addition to his work with the deaf, which advocated the oral method as the preferred mode of training throughout most of Europe, Heinicke promoted the phonetic method of teaching reading and argued his conviction that concrete experiences should precede the teaching of abstractions.