What fundamental claim about human nature did Thomas Hobbes make?
Hobbes's most important claim about human nature is that it is inherently bad. Hobbes believed that human beings were not naturally meant to live together in society because they were essentially too selfish.
To Hobbes, people are, by nature, likely to come into conflict with one another due to their inherent selfishness. This is why he famously argued that life in the state of nature was "nasty, brutish and short." Because of this inherent badness, people need to be controlled relatively harshly. It is for this reason that Hobbes believed that socieites needed to be headed by strong despots.
Hobbes's basic claim about human nature, then, is that human nature is inherently selfish.