Greatest Happiness Principle
Dictionary Definition: The ethical principle that an action is right in so far as it promotes the greatest happiness of the greatest number of those affected
Acts are seen as moral if they cause happiness for the greatest number.
More pleasure. Less Pain
In order for the action to be moral it must be the optimal choice in increasing utility and minimizing pain.
Bentham equated happiness with pleasure and the absence of pain. This was an empirical observation - people desire pleasure and seek to avoid pain.