I got to be in Spain for the spring of 2017, where I taught at Francisco de Vitoria University.

One thing that makes Francisco de Vitoria impressive was his response to indigenous Americans in the Spanish Empire.  A bit of a fanciful comparison might be thinking about how we would respond if we actually did discover new life forms on a planet in another solar system.  No one was expecting new continents between Europe and Asia, much less any new types of cultures.  Was this Asia or new land?  Were they people?  If so, did they have souls or rights?  His book on this remains worth reading.