Al-Jawab al-Sahih Liman Baddala Din al-Masih is a work authored by Shaykh al-Islam Ibn Taymiyyah in refutation of a treatise originating from Qubrus by a Christian monk called Paul of Antioch who attempted to argue for Christianity by both reason and revelation (i.e. using the Qur'an itself) and dismissing that the call of Islam is applicable to them, the Christians. Ibn Taymiyyah also intended this work as a general invitation to Christians to Islam, beyond the specific purpose for which it was mainly written.
PART 1. The universal nature of Muhammad ﷺ's prophethood and explanation of the reason for the writing of the treatise and indication that the manner of straying of the innovators from Islam is similar to the manner of straying of the Christians from the deen of the Messiah, Jesus, son of Mary عليه السلام.
PART 2. Addressing the use of Qur'anic verses as evidence in order to legitimize the religion of the Christians, by explaining the true nature of prophethood and revelation. Both Christ and Muhammad ﷺ were sent to call the people to pure monotheism in an era where many had departed from it.
PART 3. Bringing proofs for the universality of the prophethood of Muhammad ﷺ from the Qur'an and that whatever arguments are adduced to support the following of christ (transmission, miracles etc.), then the evidence for following Muhammad ﷺ with respect to the same is more overwhelming and hence more worthy of being followed.