Twenty

Bigger than a breadbox? No
In your skull? Yes
Looks like a cabbage? No
In your mind? Yes
All in your mind? No
Involve memory? No
Anyone I know? No
Would I find it in a supermarket? No
In a graveyard? No
At the State Fair? No
Is it alive? Yes
Do the pious seek it? No
Referenced by Lucretius? No
By Aristotle? Yes
Is it a jet engine? No
Atlantis? No
Does it fly? Yes
Is it a jet engine? No
I already asked that, can I take that back? No
Is it a catharsis? No