Speedy Jim wrote:
You'll have to squeeze a sharp knife blade between
toilet and floor and work all the way around.
Try different blades to see what works best.
Maybe a utility knife to start with.
A hacksaw blade (in a holder or a gloved hand)
may work too.

I've been told that alcohol or mineral spirits may help soften it up.
Might that damage the finish of the tiles around the toilet base? If I
use such chemicals to clean off the residue after removing the toilet
from the floor, might they damage the porcelain?
If the porcelain gets a hairline crack from all this work, can it be
sealed or do I have to buy a new toilet?