What are some of the underlying assumptions that guide the theoretical paradigms of realism?

Realism and Liberalism are the two paradigms with the longest history and have been in dialogue with each other over the longest period of time. Watch the following two videos about our first two paradigms:

https://www.youtube.com/watch?v=RXllDh6rD18&list=PLhQpDGfX5e7C6FA5IYU3VPYN7kWHl1mxQ (Links to an external site.)

https://www.youtube.com/watch?v=7D5FNrqT5dM&list=PLhQpDGfX5e7C6FA5IYU3VPYN7kWHl1mxQ (Links to an external site.)

What are some of the underlying assumptions that guide the theoretical paradigms of realism? Of liberalism? Where do the paradigms differ? Where do the paradigms have similarities? How do the two paradigms regard competition and cooperation in the international system?