Compard with the late ninteent century social darwinist view of the world, voltaires view in the passage is

I believe the answer is: less accepting of the idea that humans are rational animals

He believes that human are animals that completely have to restraint themselves from irrational/animalistic instinct.
He doesn't buy the notion that humans are inherently good like what being preached by religious establishments, which make him regarded as the enemy of the church at that time

What document are you referring to