Jeremy Bentham was a firm believer and the inventor of 'utilitarianism' - the general view that the best decision is the one that brings about the most happiness or 'utility' for the most amount of people. In this way he defined what "good" really is.
Utilitarianism was Bentham's greatest achievement.
He is quoted to say "nature has placed mankind under the governance of two sovereign masters, pain and pleasure" and therefore believes that good is what increases pleasure and bad is what increases pain.
For example, given the choice between killing one man to save 1000 equal men or not doing anything at all, a utilitarian would argue that it is more moral to kill that one man in order to save the 1000 because then the 1000 men will go on to live and contribute more happiness to the world than the one man would have.
This is in contrast to deontology which Bentham strongly disagreed with - the belief that actions are always right or always wrong e.g. it is immoral to kill the one man in the example, even if it would cause 1000 to die. Bentham would argue that deontology is wrong because not killing that one man is equal to killing 1000 and therefore it is 1000x the crime of murdering just one man.
Bentham believed that utilitarianism is the foundation of what ethics should be: "ethics at large may be defined, the art of directing men's actions to the production of the greatest possible quantity of happiness." (Bentham, Introduction to the Principles of Morals and Legislation)
Jeremy Bentham included animals in with his utilitarian approach on the grounds that they, like humans, could suffer and therefore need to be accounted for during decisions.
Bentham spent most of his life reforming the legal system at the time (born: 1748 died:1832) and trying to improve conditions for the people.
Bentham made prisons more hospitable.
Bentham campaigned for free education and greater democracy.
Bentham wanted there to be minimum wage, guaranteed employment, and improved working conditions.
Bentham supported sickness benefit and old age insurance.
He supported the benefits of what the Welfare State would bring, more than 100 years before it came about.
The embalmed and preserved Jeremy Bentham at University College, London | Source
Bentham completely rejected the idea of a God and said that humans need to work out their own moral beliefs based on rational evidence.
He said that we need to "Investigate; Legislate; Inspect" to bring about social reform.
Unhappy with the fact that universities were all controlled by religious bodies that limited access based upon religious belief, Jeremy Bentham helped to found the secular University College, London where in a last act of utilitarianism, he still rests embalmed today.
"The business of government is to promote the happiness of the society by punishing and rewarding." (Bentham, Introduction to the Principles of Morals and Legislation)
It was the dread of evil, not the hope of good that first cemented societies together. (Bentham, Introduction to the Principles of Morals and Legislation)
There are four distinguishable sources from which pleasure and pain are in use to flow: considered separately, they may be termed the physical, the political, the moral, and the religious: and inasmuch as the pleasures and pains belonging to each of them are capable of giving a binding force to any law or rule of conduct, they may all of them be termed sanctions. (Bentham, Introduction to the Principles of Morals and Legislation)
Do you agree with Jeremy Bentham's utilitarianism?