Final answer:
Postmillennialists believed that the preaching of the gospel, with its education and reforms, would bring in the millennial kingdom and this belief influenced missionary strategies and the expansion of missionary work.
Step-by-step explanation:
The belief in postmillennialism had a significant effect on missionary philosophy. Postmillennialists believed that the preaching of the gospel, with its education and reforms, would bring in the millennial kingdom, meaning that the second coming of Christ would be ushered in by the efforts of missionaries and the spread of Christianity. This belief influenced missionary strategies and encouraged the expansion of missionary work to different parts of the world in order to hasten the arrival of the millennial kingdom.