The apostle Paul said, “I have become all things to all men, that I might by all means save some” (I Cor 9:22). For example, he would sometimes take measures to show the Jewish people that he was not attacking the law of Moses when preaching about Jesus Christ (Acts 16:3; 18:18; 21:20-26).
We ought to make ourselves accessible and to meet people where they are. The purpose in evangelism, of course, is to create opportunities to share the saving message with unbelievers. This attitude is especially important when it comes to reaching out to others who hold views different than our own on non-essential doctrine, such as the flat earth model of the world.
Those who believe in a flat earth have been growing in number recently. When attempting to research their beliefs, I was presented with a wall of articles that outright ridiculed and demeaned those in the camp. I found that sad and unhelpful.
I will attempt to explain the flat earth position, though there are competing theories within their camp. One organization that I referenced was the Flat Earth Society,i though there are other popular speakers on this topic, such as Mark Sargent,ii Eric Dubay, and Rob Skiba. Those who believe in a flat earth do not hold that it is perfectly flat. There are of course mountains and hills and changes in elevation. They hold that the earth constitutes a flat plane, with the sun, moon and stars forming a dome above it. Magnetic north is located at the center-point of the plane, with east and west forming concentric circles around the center. In other words, if a person were to head perfectly east, they would circle around the center of the flat earth plane and eventually end up where they started. Magnetic south radiates out toward the edges of the plane. Antarctica, some hold, is an ice wall that forms the edges of the flat earth, and either terminates and connects to the sky dome, or expands out infinitely. The sun and moon are held to be much closer to the earth and are roughly equivalent in size. There are a lot of competing views and different theories regarding all I have described, but this should give you a general overview of some of their beliefs.iii
The Grace Evangelical Society does not hold to the flat earth model. Even so, it is possible for someone to believe in a flat earth and be regenerated. In fact, this topic is wholly irrelevant when it comes to receiving everlasting life. The only requirement is to believe in Jesus Christ for everlasting life (John 3:16, 6:47). It is a free gift given by grace through faith, apart from works (Eph 2:8-9). It also follows, then, that a person can be saved and believe in a round earth. In other words, the shape of the earth is not a heaven or hell issue.
In my experience, people who believe in a flat earth hold strongly to it. When discussing the topic with them, I start by asking questions to better understand their position. I also do this because I have an important objective in mind: to find an opportunity to share the saving message with them. They will be much more receptive and willing to hear what I have to say if I show that I am not seeking to ridicule or demean them.
Personally, I can relate to those in the flat earth movement, as I also hold views that are often mocked by the world. For one, I believe in the death, burial, and resurrection of the Lord Jesus Christ, and I believe in Him for everlasting life. Much of the world does not. In addition, I believe in the literal creation account of Genesis as well as a young earth model. Sadly, some in the scientific community ridicule such beliefs just as much as they would the flat earth view.
My point is that we should not be condescending or rude when broaching the topic, especially if our audience has not yet believed in the saving message. Our primary motivation should be to create opportunities for them to believe the promise of everlasting life.
As for those who believe in a flat earth, what is your primary focus when evangelizing? In my opinion, it should not be to get your audience to believe in a flat earth. The shape of the earth has nothing to do with the promise of everlasting life. If one were to lead with the flat earth topic, it could seriously hinder attempts at evangelizing and shut a person off from hearing about the promise of everlasting life entirely.
We should be careful not to equate side issues with the saving message. For instance, when attempting to evangelize others, I do not lead with or include my belief in a young earth. I do not want to present people with an unnecessary stumbling block. If the topic is brought up by my audience naturally, I would be careful to explain that one can believe in the promise of everlasting life in Jesus Christ without believing in a young earth. We err when we attempt to add conditions to the saving message.
What about interactions between fellow believers who disagree on this topic? It is simple: be respectful, loving, and courteous (I Pet 3:8-9; Heb 13:1). Engage in a healthy debate without seeking to offend one another.
Treat others as you would like to be treated (Matt 7:12) and focus on creating opportunities for people to believe in the saving message. When evangelizing, avoid bringing up unnecessary, controversial beliefs that have no bearing on the saving message or the core doctrines of the faith. I think these are good goals to have and will help us in reaching others.
i https://theflatearthsociety.org/home/
ii https://www.youtube.com/@markksargent
iii For arguments for a spherical earth, please see the following Wikipedia page: https://en.wikipedia.org/wiki/Empirical_evidence_for_the_spherical_shape_of_Earth