Today, at least in the west, we take it for granted that not hurting other people is the foundation of being a good person. It's obvious though that this wasn't always the case. In bygone eras things like treason, betrayal, and ideological impurity were regarded as the highest crimes and people seemed to have a very blithe attitude towards human suffering.
In the middle ages, even someone who was regarded as enlightened, like Thomas Moore, endorsed burning at the stake for heresy.
So what changed? How did we come to start taking human pain so seriously when just a few centuries ago torture didn't seem to be much of a big deal?
Other people might have fuller answers, but you might enjoy my earlier answer, "For much of European history, criminal punishment was extraordinarily brutal by today's standards, with mutilation and death far from uncommon. What led to the decline of violent punishment in the modern era?"