Six words, but in them is a great part of the difference between Catholics and those who oppose them:
To obey God is perfect freedom.
Our Protestant brothers and sisters seem to have a lot of difficulties with abstract concepts. It seems like in many of these discussions Catholics are discussion the beauty of sunsets and rainbows with the color blind.
Let's take the bone that seems to be sticking in their craw on this thread, "Purgatory". The concept of purgation as a means of internal cleansing the was well established within the Mediterranean cultures. "Purgatory" quite simple means a place where "purgation" or purification takes place. Theological or spiritual cleansing may be foreign to some, but it was a common theme in both the Old and New Testaments.
In the ancient Roman and Mediterranean cultures purgation, or a purification, was a very common practice in food preparation (snails, titmice, etc.) in which the contents of the digestive tract was cleansed prior to cooking and eating for obvious reasons. Similarly, purgation was a common treatment for many illnesses. Anyone who has had a child with their stomach pumped knows it is still a valid medical practice. Purgation was a long held practice for funerary purgation throughout the ancient world and even today modern embalming uses similar practices. The purgation of criminals was even commonly attempted with sulfur and onions.
So, to a Catholic, like first or second century Christian, the concept of purgatory is not alien or foreign and is actually well grounded and understood.