You don’t have to be a botanist to know the reason you can’t pick grapes from thorn bushes is that a plant only produces fruit after its own nature. An apple hangs on a tree because that tree has an inner apple nature. And Jesus said it doesn’t matter what a person says, you must examine their fruit—their lifestyle—to determine their true nature. I can say anything. For instance, “I’m a car. I’m a car. Beep. Beep.” But just saying it doesn’t make me a car. I don’t have a car nature on the inside, so there is no car exterior. Likewise, I can say, “I’m a Christian! I’m a Christian!” But don’t take my word for it, look to see if I have the nature of Christ displayed in my life.