Jeremy Bentham wrote An Introduction to the Principles of Morals and Legislation in 1870, and the book title is a good description of what it is about. In his utilitarian philosophy, Bentham explores how human society would function if humans sought to make laws governing their pleasures.

In Bentham's mind, morals should naturally develop from the pleasure principle, since he believed that all we do, we do because we are seeking pleasure, both as individuals and groups.

To this end, the book reviews the major pleasures we seek in life, and how laws to regulate and distribute those pleasures would function. He asks, and answers, the question: what kind of system of laws would develop if we acknowledged our pleasure-seeking ("utilitarian") drives?

The book details how to measure various -- common, everyday -- sources of pleasure and pain. This is important because without quantifying what constitutes pleasure, how could a law limit or encourage a certain pleasure?

The twin goals of pleasure are happiness and usefulness. Because we like to be happy and feel good, it is also useful to do so. Bentham speculates on what qualities of pleasure are important for devising metrics, including intensity, duration and degree of predictability (or certainty).

The reason this book is called "An Introduction" is because the author believes that with careful analysis, or real knowledge of what pleasure is, humans can develop sensible laws to both contain it and utilize. The author details where pleasure and pain originate, and the different circumstances that affect pleasure and pain. For example, in Chapter 6 he discusses health, strength, firmness of mind, steadiness, and a host of other personal qualities that influence how pleasure is both attained and experienced.

Bentham applies his principles in the context of English laws, such as English common law, and discusses current understanding of what "rights" are under the law. In his analysis, he does not find many instances in which common law works well with the pleasure principle; most laws are not utilitarian and punish individuals for natural pleasure-seeking habits.

Examples of utilitarian laws in modern day society are found in places where pleasure is acknowledged to be natural and good, and where a utilitarian viewpoint has been taken seriously. The best example in Western society is Holland (The Netherlands), where pleasures that are also considered vices, such as sex and drugs, have been regulated rather than outlawed. For example, in Holland prostitution is legal but well-regulated to contain the spread of disease; marijuana and other drugs are legal but contained to ensure public safety.

In the US, the Puritan strain that influenced the Founding Fathers views pleasure as suspect, wrong, and even evil - and thus in the US, we have developed laws that don't acknowledge the natural human desires for sex and drugs (for example).

Current legislation to make marijuana legal (as alcohol is) face an uphill battle, partly for the lack of utilitarianism in US legislative principles and practice.

Bentham attempts to have a frank discussion of how we can recognize human behavior for what it is, rather than what we would like it to be.