thumb|left|1599 engraving by Hendrik HondiusI Vermigli is best known for his polemics against the Catholic doctrine of transubstantiation and for the Reformed doctrine of "sacramental presence". He argued that transubstantiation, the belief that the substance of bread and wine are changed into Christ's body and blood, was not based on any argument from scripture. He also argued on the basis of Chalcedonian Christology, that because Christ retained his divine nature when he became man (the divine nature was added to the human nature rather than his human nature being made divine), the substance of the bread and wine remain the same rather than being changed into the substance of Christ's body and blood. Finally, he used the analogy of the believer's union with Christ against the idea of transubstantiation. Because believers retain their human nature even though God has joined them with Christ, it follows that the Eucharistic elements do not need to be transformed to be Christ's body. Instead of the substance of the elements changing into Christ's flesh, Vermigli emphasised the action of the sacrament as an instrument through which Christ is offered to the partaker. He also disagreed with the Anabaptist belief that the Eucharist is simply symbolic or figurative, a view called memorialism or tropism.
thumb|left|1599 engraving by Hendrik HondiusI Vermigli is best known for his polemics against the Catholic doctrine of transubstantiation and for the Reformed doctrine of "sacramental presence". He argued that transubstantiation, the belief that the substance of bread and wine are changed into Christ's body and blood, was not based on any argument from scripture. He also argued on the basis of Chalcedonian Christology, that because Christ retained his divine nature when he became man (the divine nature was added to the human nature rather than his human nature being made divine), the substance of the bread and wine remain the same rather than being changed into the substance of Christ's body and blood. Finally, he used the analogy of the believer's union with Christ against the idea of transubstantiation. Because believers retain their human nature even though God has joined them with Christ, it follows that the Eucharistic elements do not need to be transformed to be Christ's body. Instead of the substance of the elements changing into Christ's flesh Vermigli emphasised the action of the sacrament as an instrument through which Christ is offered to the partaker. He also disagreed with the Anabaptist belief that the Eucharist is simply symbolic or figurative, a view called memorialism or tropism.