Freud: id + pleasure principle
The id exists from birth and is in unconscious mind. It is the origin of the energy that motivates our behaviour, including aggression, instincts, impulses or drives that are socially unacceptable
id obeys the pleasure principle - demands immediate gratification of its desires without considering other factors liken social reality
This makes aggression unavoidable and inevitable - we can't eradicate it so we should direct it (this is what ego does)