For a start, you have to make clear if they are two-place or one-place words. If a sentence strikes a person as ungrammatical, and most of the people in his society as ungrammatical, is that pretty good evidence that that sentence is ungrammatical? Of course it is; indeed, that’s about as strong evidence for that as I can imagined. If a technology strikes a person as impossible, and most of the people in his society as physically impossible, is that pretty good evidence that that technology is impossible? Not very: even Kelvin thought Heavier-than-air flying machines were impossible. Now, is unnatural more like ungrammatical or more like impossible? That depends on what unnatural means.
For a start, you have to make clear if they are two-place or one-place words. If a sentence strikes a person as ungrammatical, and most of the people in his society as ungrammatical, is that pretty good evidence that that sentence is ungrammatical? Of course it is; indeed, that’s about as strong evidence for that as I can imagined. If a technology strikes a person as impossible, and most of the people in his society as physically impossible, is that pretty good evidence that that technology is impossible? Not very: even Kelvin thought Heavier-than-air flying machines were impossible. Now, is unnatural more like ungrammatical or more like impossible? That depends on what unnatural means.