What is your motive for staying out of the farming profession? And the motive for that? And so on?It's immoral not to be a farmer since, if no one was a farmer, we'd all starve
Keep doing this until you find the metaphysical assumption (we've all got a set of those) on which it is based.
Now ask, "What would it be like if everyone lived by this assumption?"
Does it create a contradiction?
If so, the CI says you should drop that assumption. And if the answer to the first question is distasteful to you - that also means you should drop the assumption.
Maybe not precise but it gives you the gist of the CI.