Are grapes gathered from thornbushes, or figs from thistles? So, every healthy tree bears good fruit, but the diseased tree bears bad fruit.?

Question

Even a young man is known by his actions--by whether his behavior is pure and upright.

Answer 1

While proverbs are interesting analogies or metaphors, they often do fail in actual practice.  The failure with this one is the logical leap from "I don't get some fruit from some nasty plants" to "therefore every healthy tree bears fruit".  That was not demonstrated.  Non sequitur.

Answer 2

So, are you saying blackberries are a bad fruit, or are you simply trying to make a bad analogy you hope to use to somehow disprove the science of biology?  That's not how ideas are overturned in the sciences - you have to find better solid evidence for your idea, not cast doubt on existing explanations.

Answer 3

grapes come from grape vines, and figs come from fig trees.

What does this have to do with math?