Throughout history, there have been many theological ideas. Many are based on Biblical truth and many are not. How can you know the difference? There's an old saying: "If it walks like a duck, and it quacks like a duck, it must be a duck."
For the purpose of this discussion, let's say that any idea that doesn't follow scripture is a "duck."
All of these ducks cause division among God's people, hurt feelings, split churches, cause His people to stop having fellowship with each other. That is BAD fruit. In Matthew 7, Jesus says that no good tree can produce bad fruit, and no bad tree can produce good fruit. "Fruit" is just another way of saying "the end result." You plant an apple seed, the end result is apples. If these different ideas produce bad fruit, they are therefore a bad tree. I didn't make this up, look it up for yourself.
Take for example, the idea that you can lose your salvation if you sin bad enough. There are some verses in Scripture that might seem to indicate this might be true (if you ignore all the other verses to the contrary). However, the division and anger and split this has caused among God's people is BAD FRUIT. How about the idea that you MUST speak in tongues in order to truly worship. This idea caused many to leave their church and join another... BAD FRUIT. Both of these ideas are obviously false teachings according to Scripture... both of them are "ducks."
Some ideas, however, are little more complicated. The Scripture is perhaps unclear sometimes. The most obvious example is what the Scripture says about the end times. There are several different theories that both seem to be backed by Scripture. So how do you know what is the right one? If it walks like a duck, and it talks like a duck, it must be a duck.
In other words, any idea about the Bible or God or Jesus, etc. that causes people to divide, split, or get angry must be rejected as false. Why? No good tree can produce bad fruit.
