issued by Pope Gregory XVI
regarding the institution of slavery
. Issued on December 3, 1839 as a result of a broad consultation among the College of Cardinals
, the bull resoundingly denounces both the slave trade and the continuance of the institution of slavery.
In 1839, Pope Gregory XVI wrote In Supremo Apostolatus, an historic Papal Bull
condemning the international slave trade. The Bull outlines the history of Church attitudes to slavery, beginning with the Apostles who tolerated slavery but called on masters to "act well towards their slaves...
There is one living spirit, prevalent over this world ... which assumes a multitude of forms according to subordinate laws. There is one thinking sensible principle allied to one kind of organic matter. 
We can allow satellites, planets, suns, universe, nay whole systems of universe, to be governed by laws, but the smallest insect, we wish to be created at once by special act.
Our faculties are more fitted to recognize the wonderful structure of a beetle than a Universe.
I feel most deeply that this whole question of Creation is too profound for human intellect. A dog might as well speculate on the mind of Newton! Let each man hope and believe what he can.
Physiological experiment on animals is justifiable for real investigation, but not for mere damnable and detestable curiosity.
I love fools' experiments. I am always making them.