These two passages are not in conflict at all. The second is mostly an example of the first. The passage in the second stating
So he investigated, and eventually discovered that they had started throwing the onion in years ago to test the temperature of the varnish: if it was hot enough, the onion would fry.
is simply a specific example of
Then, when you can come back and tell me that you do see the use of it, I may allow you to destroy it.
The use of the onion was found, and now it can be removed with much greater confidence that no ill effect will result.
The only real difference (not explicitly stated) between the anecdotes and corresponding principles is that there are often other ways to verify that no ill effect will result without needing to discover the original purpose. The “more intelligent reformer” of Chesterton’s Fence will presumably continue to object until the purpose is found, while an “onion” reformer might explicitly conduct tests on the reformed varnish recipe to ascertain whether it is as good, better, or worse.
These two passages are not in conflict at all. The second is mostly an example of the first. The passage in the second stating
is simply a specific example of
The use of the onion was found, and now it can be removed with much greater confidence that no ill effect will result.
The only real difference (not explicitly stated) between the anecdotes and corresponding principles is that there are often other ways to verify that no ill effect will result without needing to discover the original purpose. The “more intelligent reformer” of Chesterton’s Fence will presumably continue to object until the purpose is found, while an “onion” reformer might explicitly conduct tests on the reformed varnish recipe to ascertain whether it is as good, better, or worse.