Philosophy: are we quite sure it's the mushroom growing out of the frog? Reminds me of a joke: A policeman walks into a doctor's surgery with a pig on his head

Philosophy: are we quite sure it's the mushroom growing out of the frog? Reminds me of a joke: A policeman walks into a doctor's surgery with a pig on his head. The doctor says "errr... I think I can see the problem". The pig says "yes, I've got this thing growing on my foot".